iris: Split iris_resource_alloc_aux to enable aux modifiers

iris: Split iris_resource_alloc_aux to enable aux modifiers

Reworks:

 * If the aux-state is not ISL_AUX_STATE_AUX_INVALID, then use memset
   even when memset_value is zero. The hiz buffer initial aux-state
   will be set to invalid, and therefore we can skip the memset. But,
   for CCS it will be set to ISL_AUX_STATE_PASS_THROUGH, and therefore
   the aux data must be cleared to 0 with the memset. Previously we
   would use BO_ALLOC_ZEROED with the CCS aux data, so this memset
   wasn't required. Now, the CCS aux data may be part of the main
   surface. We prefer to not use BO_ALLOC_ZEROED excessively, so the
   memset is needed for the CCS case. (Nanley)

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>