nvfuser + prim stack generated illegal PTX code on hardware with sm <= 70
Labels: triaged, module: nvfuser, module: primTorch

### 🐛 Describe the bug

```
import torch
  
from torch._prims.context import TorchRefsNvfuserCapabilityMode, TorchRefsMode, _is_func_unsupported_nvfuser
from torch.fx.experimental.proxy_tensor import make_fx
from torch._prims.executor import execute

dtype = torch.bfloat16
# dtype = torch.float16

x = torch.rand(5, device="cuda").to(dtype)

def fn(x):
    return (x + 1.0).relu()

with TorchRefsNvfuserCapabilityMode():
    nvprim_gm = make_fx(fn)(x)
    print(nvprim_gm.graph)

for i in range(5):
    o = execute(nvprim_gm, x, executor="nvfuser")

print(o)
```

gives the error message:
```
CUDA NVRTC compile error: ptxas application ptx input, line 55; error   : Feature '.bf16' requires .target sm_80 or higher
ptxas application ptx input, line 55; error   : Feature 'cvt with .bf16' requires .target sm_80 or higher
ptxas fatal   : Ptx assembly aborted due to errors

```

### Versions

Collecting environment information...
PyTorch version: 1.13.0a0+gitce7177f
Is debug build: False
CUDA used to build PyTorch: 11.7
ROCM used to build PyTorch: N/A

OS: Ubuntu 20.04.4 LTS (x86_64)
GCC version: (Ubuntu 9.4.0-1ubuntu1~20.04.1) 9.4.0
Clang version: Could not collect
CMake version: version 3.24.1
Libc version: glibc-2.31

Python version: 3.8.13 (default, Mar 28 2022, 11:38:47)  [GCC 7.5.0] (64-bit runtime)
Python platform: Linux-5.4.0-92-generic-x86_64-with-glibc2.17
Is CUDA available: True
CUDA runtime version: 11.7.64
GPU models and configuration: 
GPU 0: Tesla V100-SXM2-16GB
GPU 1: Tesla V100-SXM2-16GB
GPU 2: Tesla V100-SXM2-16GB
GPU 3: Tesla V100-SXM2-16GB
GPU 4: Tesla V100-SXM2-16GB
GPU 5: Tesla V100-SXM2-16GB
GPU 6: Tesla V100-SXM2-16GB
GPU 7: Tesla V100-SXM2-16GB

Nvidia driver version: 470.82.01
cuDNN version: Probably one of the following:
/usr/lib/x86_64-linux-gnu/libcudnn.so.8.4.0
/usr/lib/x86_64-linux-gnu/libcudnn_adv_infer.so.8.4.0
/usr/lib/x86_64-linux-gnu/libcudnn_adv_train.so.8.4.0
/usr/lib/x86_64-linux-gnu/libcudnn_cnn_infer.so.8.4.0
/usr/lib/x86_64-linux-gnu/libcudnn_cnn_train.so.8.4.0
/usr/lib/x86_64-linux-gnu/libcudnn_ops_infer.so.8.4.0
/usr/lib/x86_64-linux-gnu/libcudnn_ops_train.so.8.4.0
HIP runtime version: N/A
MIOpen runtime version: N/A
Is XNNPACK available: True

Versions of relevant libraries:
[pip3] bert-pytorch==0.0.1a4
[pip3] functorch==0.3.0a0+ce7177f
[pip3] mypy-extensions==0.4.3
[pip3] numpy==1.21.2
[pip3] pytorch-transformers==1.2.0
[pip3] torch==1.13.0a0+gitce7177f
[pip3] torch-struct==0.5
[pip3] torchdynamo==1.13.0.dev0
[pip3] torchfile==0.1.0
[pip3] torchmetrics==0.9.3
[pip3] torchrec-nightly==2022.8.17
[pip3] torchtext==0.14.0a0+72966f0
[pip3] torchvision==0.14.0a0+c3dc255
[pip3] torchx-nightly==2022.8.17
[conda] bert-pytorch              0.0.1a4                   dev_0    <develop>
[conda] functorch                 0.3.0a0+ce7177f           dev_0    <develop>
[conda] magma-cuda110             2.5.2                         1    pytorch
[conda] mkl                       2019.1                      144
[conda] mkl-include               2019.1                      144
[conda] nomkl                     3.0                           0
[conda] numpy                     1.21.2                   pypi_0    pypi
[conda] pytorch-transformers      1.2.0                    pypi_0    pypi
[conda] torch                     1.13.0a0+gitce7177f           dev_0    <develop>
[conda] torch-struct              0.5                      pypi_0    pypi
[conda] torchdynamo               1.13.0.dev0               dev_0    <develop>
[conda] torchfile                 0.1.0                    pypi_0    pypi
[conda] torchmetrics              0.9.3                    pypi_0    pypi
[conda] torchrec-nightly          2022.8.17                pypi_0    pypi
[conda] torchtext                 0.14.0a0+72966f0           dev_0    <develop>
[conda] torchvision               0.14.0a0+c3dc255           dev_0    <develop>
[conda] torchx-nightly            2022.8.17                pypi_0    pypi

cc @ezyang @mruberry @ngimel