efifb: BGRT: Do not copy the boot graphics for non native resolutions

On x86 some firmwares use a low non native resolution for the display when
they have shown some text messages. While keeping the bgrt filled with info
for the native resolution. If the bgrt image intended for the native
resolution still fits, it will be displayed very close to the right edge of
the display looking quite bad.

This commits adds a (heuristics based) checks for this and makes efifb
not show the boot graphics when this is the case.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>