drm/i915: Sink rate read should be saved in deca-kHz

The sink rate read from supported link rate table is in KHz as per spec
while in drm, the saved clock is in deca-KHz. So divide the link rate by
10 before storing.

Reading of rates was added by:
commit fc0f8e25 ("drm/i915/skl: Read sink supported rates from edp
panel")

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Sonika Jindal <sonika.jindal@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>