drm/i915/perf: Update handling of MMIO triggered reports

On XEHP platforms user is not able to find MMIO triggered reports in the
OA buffer since i915 squashes the context ID fields. These context ID
fields hold the MMIO trigger markers.

Update logic to not squash the context ID fields of MMIO triggered
reports.

Fixes: 7eeaedf7 ("drm/i915/perf: Determine context valid in OA reports")
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/20231219000543.1087706-1-umesh.nerlige.ramappa@intel.com