drm/i915: Refactor non-EDID fixed mode duplication

drm/i915: Refactor non-EDID fixed mode duplication

All the non-EDID fixed mode functions basically do the exact
same thing. Let's refactor the common bits into a shared
function.

There are minor differences on how the mode types are populated,
whether the display info physical size is updated, and the debug
print. The differences are purely accidental, so unifying them is
actually a good thing.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220331112822.11462-4-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>