media: vimc: Add missing {RGB,BGR,GBR}888 media bus codes

Add missing RGB888_*, BGR888_* and GBR888_* media bus codes in the
vimc_pix_map_list. Since there is no GBR24 pixelformat, use the RGB24
pixelformat for MEDIA_BUS_FMT_GBR888_1X24.

Acked-by: Helen Koike <helen.koike@collabora.com>
Co-developed-by: Vitor Massaru Iha <vitor@massaru.org>
Signed-off-by: Vitor Massaru Iha <vitor@massaru.org>
Signed-off-by: Nícolas F. R. A. Prado <nfraprado@protonmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>