drm/debug: Expose connector VRR monitor range via debugfs

drm/debug: Expose connector VRR monitor range via debugfs

[Why]
It's useful to know the min and max vrr range for IGT testing.

[How]
Expose the min and max vfreq for the connector via a debugfs file
on the connector, "vrr_range".

Example usage: cat /sys/kernel/debug/dri/0/DP-1/vrr_range

v2:
* Fix the typo in max_vfreq (Manasi)
* Change the name of node to i915_vrr_info so we can add
other vrr info for more debug info (Manasi)
* Change the VRR capable to display Yes or No (Manasi)
* Fix indentation checkpatch errors (Manasi)
v3:
* Remove the unnecessary debug print (Manasi)
v4:
* Rebase
v5:
* Rename to vrr_range to match AMD debugfs
v6:
* Rebase (manasi)
v7:
* Fix cmpilation due to rebase
v8:
* Move debugfs node creation logic to DRM (Emil)
* Remove AMD specific logic (Emil)
v9:
* Separate patch for removal of AMD specific logic (Manasi)

Signed-off-by: Bhanuprakash Modem <bhanuprakash.modem@intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Harry Wentland <harry.wentland@amd.com>
CC: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200622142519.16214-3-bhanuprakash.modem@intel.com