glsl: Disable tree grafting optimization for shared variables

glsl: Disable tree grafting optimization for shared variables

Fixes:
 * dEQP-GLES31.functional.compute.basic.shared_atomic_op_multiple_groups
 * dEQP-GLES31.functional.compute.basic.shared_atomic_op_multiple_invocation
 * dEQP-GLES31.functional.compute.basic.shared_atomic_op_single_group
 * dEQP-GLES31.functional.compute.basic.shared_atomic_op_single_invocation

From https://android.googlesource.com/platform/external/deqp

Reported-by: Ilia Mirkin <imirkin@alum.mit.edu>
Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Tested-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>