drm/xe/oa/uapi: Expose MERT OA unit

drm/xe/oa/uapi: Expose MERT OA unit

A MERT OA unit is available in the SoC on some platforms. Add support
for this OA unit and expose it to userspace. The MERT OA unit does not
have any HW engines attached, but is otherwise similar to an OAM unit.

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Link: https://patch.msgid.link/20251205212613.826224-2-ashutosh.dixit@intel.com