drm: Allow override_edid to override the firmware EDID

drm: Allow override_edid to override the firmware EDID

IMO the override_edid should override any default EDID for the
connector, whether that came in via the connector helper ->get_modes()
vfunc or via the firmware EDID mechanism.

Cc: Thomas Wood <thomas.wood@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.kernel.org/patch/7822361/
Git-Commit: 0e8578c996a33c8da9c28f8ed2d1be68694070ee
Git-repo: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Change-Id: I247c19010434473c9af9e0bb8cdeed6b335e4714
Signed-off-by: Tanmay Shah <tanmay@codeaurora.org>