nv50: don't leak heap on tls alloc failure

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
nouveau: add fast-path for constant buffer upload

Saves a memcpy, and increased threshold for push method, which is
usually better because there's no subchannel switch.
FOLD nouveau: update fences when "manually" push_cb'ing
debug prints
nouveau: clear GPU_READING/WRITING bits when syncing buffer

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
speed-up attempt by doing a direct write if dest is gart