intel/brw: ensure find_live_channel don't access arch register without sync
What does this MR do and why?
intel/brw: ensure find_live_channel don't access arch register without sync
Another architecture register that requires some care before reading.
Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Fixes: 49ee3ae9e8b ("intel/compiler: Lower FIND_[LAST_]LIVE_CHANNEL in IR on Gfx8+")