anv: Emit CS Stall before Instruction Cache flush for gen12 WA

anv: Emit CS Stall before Instruction Cache flush for gen12 WA

Before flushing the instruction cache with a pipe control, we need to
use a CS Stall pipe control.

Ref: GEN:BUG:1409226450
Rework: Add stall-at-scoreboard (Lionel)
Rework: Merge with other anvil pre-invalidate stalls (Lionel)
Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3457>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3457>