drm/fourcc: Add missing big-endian XRGB1555 and RGB565 formats

As of commit eae06120 ("drm: refuse ADDFB2 ioctl for broken
bigendian drivers"), drivers must set the
quirk_addfb_prefer_host_byte_order quirk to make the drm_mode_addfb()
compat code work correctly on big-endian machines.

While that works fine for big-endian XRGB8888 and ARGB8888, which are
mapped to the existing little-endian BGRX8888 and BGRA8888 formats, it
does not work for big-endian XRGB1555 and RGB565, as the latter are not
listed in the format database.

Fix this by adding the missing formats.  Limit this to big-endian
platforms, as there is currently no need to support these formats on
little-endian platforms.

Fixes: 6960e6da

 ("drm: fix drm_mode_addfb() on big endian machines.")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/3ee1f8144feb96c28742b22384189f1f83bcfc1a.1669221671.git.geert@linux-m68k.org