intel/blorp: Lower base_workgroup_id to zero
We don't use a base workgroup ID for BLOCS. It needs to be lowered, or else we'll assert fail when compiling the compute shader.
(Note for stable: this patch doesn't fix a bug in 4abdecce specifically, but rather is a missing patch that needed to go along with the rest of MR 20068, on whichever branches it exists on.)
Fixes: 4abdecce ("iris: Lower load_base_workgroup_id to zero")