iris: Drop depth cache flush requirement after depth clear/resolve

iris: Drop depth cache flush requirement after depth clear/resolve

From Bspec 46959, a programming note applicable to Gfx12+:

   "Since HZ_OP has to be sent twice (first time set the clear/resolve
   state and 2nd time to clear the state), and HW internally flushes the
   depth cache on HZ_OP, there is no need to explicitly send a Depth
   Cache flush after Clear or Resolve."

Signed-off-by: Sagar Ghuge <sagar.ghuge@intel.com>
Reviewed-by: Nanley Chery <nanley.g.chery@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24027>