drm/i915: Refactor VBT fixed mode handling

LVDS and eDP have essentially the same code for grabbing the
fixed mode from VBT. Pull that code to a common location.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190321132446.22394-3-ville.syrjala@linux.intel.com
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Jani Nikula <jani.nikula@intel.com>
4 files changed