drm/i915: Use the first mode if there is no preferred mode in the EDID

This matches the algorithm used by earlier kernels when selecting the
mode for the fbcon. And only if there is no modes at all, do we fall
back to using the BIOS configuration. Seamless transition is still
preserved (from the BIOS configuration to ours) so long as the BIOS has
also chosen what we hope is the native configuration.

Reported-by: Knut Petersen <Knut_Petersen@t-online.de>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=78655


Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Tested-by: Knut Petersen <Knut_Petersen@t-online.de>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
[Jani: applied Chris' "Please imagine that I wrote this correctly."]
Signed-off-by: Jani Nikula <jani.nikula@intel.com>