drm/i915/perf: Determine context valid in OA reports

When supporting OA for TGL, it was seen that the context valid bit in
the report ID was not defined, however revisiting the spec seems to have
this bit defined. The bit is used to determine if a context is valid on
a context switch and is essential to determine active and idle periods
for a context. Re-enable the context valid bit for gen12 platforms.

BSpec: 52196 (description of report_id)

v2: Include BSpec reference (Ashutosh)

Fixes: 00a7f0d7 ("drm/i915/tgl: Add perf support on TGL")
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/20230802202854.1224547-1-umesh.nerlige.ramappa@intel.com