drm/i915/perf: Fix OA filtering logic for GuC mode

With GuC mode of submission, GuC is in control of defining the context
id field that is part of the OA reports. To filter reports, UMD and KMD
must know what sw context id was chosen by GuC. There is not interface
between KMD and GuC to determine this, so read the upper-dword of
EXECLIST_STATUS to filter/squash OA reports for the specific context.

v2: Explain guc id stealing w.r.t OA use case

Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Reviewed-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221026222102.5526-2-umesh.nerlige.ramappa@intel.com