intel/eu/gen12: Implement immediate 64 bit constant encoding.

intel/eu/gen12: Implement immediate 64 bit constant encoding.

On Gen12, 64 bit immediate constants are loaded in reverse order. Lower
32 bit gets loaded from bit 96-127 and higher 32 bits from 64-95 in
instruction encoding.

Signed-off-by: Sagar Ghuge <sagar.ghuge@intel.com>
Co-authored-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Francisco Jerez <currojerez@riseup.net>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>