pan/bi: Track LOD mode even for TEXC

Redundant with the texture operation descriptor, but we don't want to
parse that in the rest of the compiler. Handling it as a pseudo-modifier
lets us share a code path with TEXS.

Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11733>
3 files changed