drm/i915/selftests: Correct frequency handling in RPS power measurement

Fix the frequency calculation by ensuring it uses the raw frequency only.
Update live_rps_power test to use the correct frequency values for logging
and comparison.

Signed-off-by: Sk Anirban <sk.anirban@intel.com>
Reviewed-by: Badal Nilawar <badal.nilawar@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250113095912.356147-2-sk.anirban@intel.com

Author: sanirban-999

drivers/gpu/drm/i915/gt/selftest_rps.c

@@ -1116,7 +1116,7 @@ static u64 measure_power(struct intel_rps *rps, int *freq)
 	for (i = 0; i < 5; i++)
 		x[i] = __measure_power(5);
 
-	*freq = (*freq + intel_rps_read_actual_frequency(rps)) / 2;
+	*freq = (*freq + read_cagf(rps)) / 2;
 
 	/* A simple triangle filter for better result stability */
 	sort(x, 5, sizeof(*x), cmp_u64, NULL);