i965: allow sampler indirects on all gens

i965: allow sampler indirects on all gens

Without this we will regress the max-samplers piglit test on Gen6
and lower when loop unrolling is done in NIR. There is a check
in the GLSL IR linker that errors when it finds indirects and
EmitNoIndirectSampler is set.

As far as I can tell there is no reason for not enabling this for
all gens regardless of whether they fully support ARB_gpu_shader5
or not.

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>