nir/validate: allow bias on nir_texop_lod
What does this MR do and why?
nir/validate: allow bias on nir_texop_lod
AGX seems to support it, and it's very convenient for implementing sampler LOD
bias together with a clamped LOD query.
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>