glsl/cs: Fix local_size_y and local_size_z

glsl/cs: Fix local_size_y and local_size_z

flags.q.local_size has 3 bits. One each for x, y and z.

Fixes piglit's:
* spec/ARB_compute_shader/linker/mismatched_local_work_sizes
* spec/ARB_compute_shader/compiler/default_local_size.comp
* spec/ARB_compute_shader/compiler/work_group_size_too_large
* spec/ARB_compute_shader/compiler/gl_WorkGroupSize_matches_layout.comp

This was regressed in 738c9c3c.

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Chris Forbes <chrisf@ijw.co.nz>