One or more engines map to a specific OA unit. All reports from these
engines are captured in the OA buffer managed by this OA unit.

Current i915 OA implementation supports only the OAG unit. OAG primarily
caters to render engine, so i915 OA uses render as the default engine
in the OA implementation. Since there are more OA units on newer
hardware that map to other engines, allow user to pass engine class and
instance to select and program specific OA units.

UMD specific changes for GPUvis support:
https://patchwork.freedesktop.org/patch/522827/?series=114023
https://patchwork.freedesktop.org/patch/522822/?series=114023
https://patchwork.freedesktop.org/patch/522826/?series=114023
https://patchwork.freedesktop.org/patch/522828/?series=114023
https://patchwork.freedesktop.org/patch/522816/?series=114023
https://patchwork.freedesktop.org/patch/522825/?series=114023

v2: (Ashutosh)
- Clarify commit message
- Add drm_dbg
- Clarify uapi description

v3: (Ashutosh)
- Remove irrelevant info from the uapi comment

v4: Ensure engine class:instance is passed together (Ashutosh)
v5: Remove unnecessary quote (Ashutosh)
Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Reviewed-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230323225901.3743681-9-umesh.nerlige.ramappa@intel.com