drm/xe/oa/uapi: Initialize OA units

Initialize OA unit data struct's for each gt during device probe. Also
assign OA units for hardware engines.

v2: Remove XE_OA_UNIT_OAG/XE_OA_UNIT_OAM_SAMEDIA_0 enum (Umesh)
    Change mtl_oa_base to 0x13000 (Umesh)
v3: Switch to drmm_ functions and other cleanups (Michal)

Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240618014609.3233427-5-ashutosh.dixit@intel.com