drm/i915/gt: Set CMD_CCTL to UC for Gen12 Onward

Cache-control registers for Command Stream(CMD_CCTL) are used
to set catchability for memory writes and reads outputted by
Command Streamers on Gen12 onward platforms.

These registers need to point un-cached(UC) MOCS index.

Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Ayaz A Siddiqui <ayaz.siddiqui@intel.com>
Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210903092153.535736-3-ayaz.siddiqui@intel.com