i965: move brw_nir_lower_gl_images call

i965: move brw_nir_lower_gl_images call

At this moment that lowering is using info coming from the
UniformStorage, so for the ARB_gl_spirv codepath, it needs to be done
after calling gl_nir_link_uniforms. As for the GLSL codepath it can
also be called later, we just move the call on both cases, to avoid
adding several shader->spirv_data checks, and keep the patch as small
as possible.

This is the first patch needed to fix the following piglit tests:

  tests/spec/arb_gl_spirv/linker/uniform/multisampler.shader_test
  tests/spec/arb_gl_spirv/linker/uniform/multisampler-array.shader_test

but fixes thousands of tests when borrowing the tests from other specs
(that needs to be done manually right now).

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