drm/i915/selftests: Implement frequency logging for energy reading validation

Add RC6 & RC0 frequency printing to ensure accurate energy
readings aimed at addressing GPU energy leaks and power
measurement failures.
Also update sleep time for RC6 mode to match RC0.

v2:
  - Improved commit message.
v3:
  - Used pr_err log to display frequency (Anshuman)
  - Sorted headers alphabetically (Sai Teja)
v4:
  - Improved commit message.
  - Fix pr_err log (Sai Teja)
v5:
  - Add error & debug logging for RC0 power and frequency checks (Anshuman)
v6:
  - Modify debug logging for RC0 power and frequency checks (Sai Teja)
v7:
  - Use pr_debug if RC0 power isn't measured but frequency is (Anshuman)
  - Improved commit message (Badal)
  - Change API to read actual frequency without applying forcewake (Badal)
  - Update sleep time for RC6 mode (Anshuman)

Signed-off-by: Sk Anirban <sk.anirban@intel.com>
Reviewed-by: Sai Teja Pottumuttu <sai.teja.pottumuttu@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/20241129154716.2764974-1-sk.anirban@intel.com