media: Add P012 and P012M video format

P012 is a YUV format with 12-bits per component with interleaved UV,
like NV12, expanded to 16 bits.
Data in the 12 high bits, zeros in the 4 low bits,
arranged in little endian order.
And P012M has two non contiguous planes.

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>