media: vimc: Support multiple media bus codes for each pixelformat

Change vimc_pix_map_list to allow multiple media bus codes to map to the
same pixelformat, making it possible to add media bus codes for which
there are no pixelformat.

Acked-by: Helen Koike <helen.koike@collabora.com>
Signed-off-by: Nícolas F. R. A. Prado <nfraprado@protonmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
[hverkuil-cisco@xs4all.nl: fix sparse warning: const u32 -> u32]
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>