drm/i915: Introduce has_media_ratio_mode

Media ratio mode (the ability for media IP to work at a different frequency
from the GT) is available for a subset of dGfx platforms supporting
GuC/SLPC. Introduce 'has_media_ratio_mode' flag in intel_device_info to
identify these platforms and set it for XEHPSDV and DG2/ATS-M.

Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220519085732.1276255-1-tvrtko.ursulin@linux.intel.com
[tursulin: fixup merge conflict]