drm/i915/display: Some code improvements and code style fixes for DRRS

It started as a code style fix for the lines above 100 col but it
turned out to simplifications to intel_drrs_set_state().
Now it receives the desired refresh rate type, high or low.

v3:
- Fixed the mode refesh rate debug message

Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210903221036.34770-1-jose.souza@intel.com