nv50: only over-allocate by a page for code

The pre-fetching doesn't go too far. Tested with over-allocating by only
a page, and didn't see any errors in dmesg. Saves ~512KB of VRAM.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Cc: 10.1 <mesa-stable@lists.freedesktop.org>
nouveau/codegen: allow tex offsets on non-TXF instructions (e.g. TXL)

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
nouveau/video: make sure that firmware is present when checking caps

Apparently some players are ill-prepared for us claiming that a decoder
exists only to have creating it fail, and express this poor preparation
with crashes (e.g. flash). Check that firmware is there to increase the
chances of there being a high correlation between reported capabilities
and ability to create a decoder.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Cc: 10.0 10.1 <mesa-stable@lists.freedesktop.org>