llvmpipe: fix caching for texture shaders.

caching only works if you check the size and store the result,
later the size is always set.

Fixes: f675e4ee8231 ("llvmpipe: Pre compile sample functions")
Reviewed-by: Konstantin Seurer <konstantin.seurer@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25648>
1 file changed