intel/fs: Lower A64 untyped r/w messages to LSC when available

intel/fs: Lower A64 untyped r/w messages to LSC when available

We set the ex_desc to 0, since the address surface type is FLAT.

v2 (Sagar Ghuge):
 - Fix message descriptor encoding

v2 (Jason Ekstrand):
 - Drop support for block messages

Co-authored-by: Sagar Ghuge <sagar.ghuge@intel.com>
Co-authored-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Sagar Ghuge <sagar.ghuge@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11600>