drm/i915: Disable PSR around cdclk changes

AUX logic is often clocked from cdclk. Disable PSR to make sure
there are no hw initiated AUX transactions in flight while we
change the cdclk frequency.

Cc: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210608085415.515342-2-gwan-gyeong.mun@intel.com