drm/i915: Call intel_opregion_notify_encoder in intel_sanitize_encoder, v2.

drm/i915: Call intel_opregion_notify_encoder in intel_sanitize_encoder, v2.

Normally this is called on a modeset, but the call is missing when
we inherit the mode from the BIOS, so make sure it's called somewhere
in hardware readout.

Changes since v1:
- Unconditionally call intel_opregion_notify_encoder. (Ville)

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180516085038.36785-1-maarten.lankhorst@linux.intel.com
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>