drm/xe/pmu: Add GT frequency events

Define PMU events for GT frequency (actual and requested). The
instantaneous values for these frequencies will be displayed.

Following PMU events are being added:
  xe_0000_00_02.0/gt-actual-frequency/              [Kernel PMU event]
  xe_0000_00_02.0/gt-requested-frequency/           [Kernel PMU event]

Standard perf commands can be used to monitor GT frequency:
  $ perf stat -e xe_0000_00_02.0/gt-requested-frequency,gt=0/ -I1000

  1.001229762       1483 Mhz  xe_0000_00_02.0/gt-requested-frequency,gt=0/
  2.006175406       1483 Mhz  xe_0000_00_02.0/gt-requested-frequency,gt=0/

v2: Use locks while storing/reading samples, keep track of multiple
clients (Lucas) and other general cleanup.
v3: Review comments (Lucas) and use event counts instead of mask for
active events.
v4: Add freq events to event_param_valid method (Riana)
v5: Use instantaneous values instead of aggregating (Lucas)
v6: Obtain fwake at init for freq events as well and use non fwake
variant method for reading requested freq to avoid lockdep issues (Lucas)
v7: Review comments (Rodrigo, Lucas)

Cc: Riana Tauro <riana.tauro@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://lore.kernel.org/r/20250331204827.2535393-1-vinay.belgaumkar@intel.com