glsl: Don't lower vector derefs for SSBOs, UBOs, and shared

glsl: Don't lower vector derefs for SSBOs, UBOs, and shared

All of these are backed by some sort of memory so if you have multiple
threads writing to different components of the same vector at the same
time, the load-vec-store pattern that GLSL IR emits won't work.  This
shouldn't affect any drivers today as they all call GLSL IR lowering
which lowers access to these variables to index+offset intrinsics before
we get to this point.  However, NIR will start handling the derefs
itself and won't want the lowering.

Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>