nv50: don't try to upload MSAA settings for BUFFER textures

nv50: don't try to upload MSAA settings for BUFFER textures

We need the MSAA scaling parameters to properly fetch samples from MSAA
textures. These are stored in the miptree which wraps all regular
textures. However it does not wrap buffer textures, so make sure to skip
them rather than accessing out-of-bounds or unmapped memory.

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/2727
Fixes: 3bd40073b98 ("nv50: add support for texelFetch'ing MS textures")
Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Cc: mesa-stable@lists.freedesktop.org
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4424>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4424>