intel/compiler: rename brw_nir_lower_glsl_images

intel/compiler: rename brw_nir_lower_glsl_images

To brw_nir_lower_gl_images, as it will be also used on the
ARB_gl_spirv codepath, that doesn't involves GLSL at all. So the
lowering is about images following the OpenGL semantics. In any case
"brw_nir_lower_opengl_images" seemed too long to me, so I just used
gl. That shortening is already used on other parts of the code.

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