drm/i915/icl: Ensure port A combo PHY HW state is correct

Make sure the HW state of the port A combo PHY is correct wrt. the
IREFGEN setting. This will force a reprogramming during init or a WARN
during uninit if the setting is incorrect.

On my ICL RVP I haven't seen this check failing and leading to a forced
reinit/WARN, but let's add it still for consistency.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190531082626.30640-1-imre.deak@intel.com