BACKPORT: media: Add BGR48_12 video format

BGR48_12 is a reversed RGB format with 12 bits per component like BGR24,
expanded to 16bits.
Data in the 12 high bits, zeros in the 4 low bits,
arranged in little endian order.

Bug: 293213303
Change-Id: I27d14a33c8e2b4847a63ea05b285786766949ebf
(cherry picked from commit da0b7a40)
[Jindong: Fixed conflicts in .rst file and v4l2-ioctl.c]
Signed-off-by: Ming Qian <ming.qian@nxp.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Jindong Yue <jindong.yue@nxp.com>