media: imx: utils: Introduce PIXFMT_SEL_IPU

Add a PIXFMT_SEL_IPU selection flag, to select only the IPU-internal
pixel formats, and move the single-entry IPU-internal pixel format
arrays into pixel_formats[]. imx_media_find_ipu_format() and
imx_media_enum_ipu_format() can now simply call find_format() and
enum_format().

The RGB32 format is both an IPU-internal format, and an in-memory format
via idmac channels that is supported by the IPUv3 driver, so it appears
twice in pixel_formats[], one with ipufmt=false for the in-memory format,
and again with ipufmt=true for the IPU-internal format.

Signed-off-by: Steve Longerbeam <slongerbeam@gmail.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>