st/mesa: Record shader access qualifiers for images

st/mesa: Record shader access qualifiers for images

They're not required to be the same as the access flag on the image
unit.  For hardware that does shader image lowering based on the
qualifier (Intel), it may be required for state setup.

v2: (by Kenneth Graunke, incorporating feedback from Marek Olšák)
 - Reduce both access and shader_access to uint16_t to avoid making
   the pipe_image_view structure larger.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>