wayland-info: Make shm printing more consistent with dmabuf

One line per format, and using the same layout.

This also removes the special case for RGB565, only ARGB8888 and
XRGB8888 need to be special-cased.

Signed-off-by: Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>
Reviewed-by: Simon Ser <contact@emersion.fr>
Reviewed-by: Olivier Fourdan <ofourdan@redhat.com>