media: vimc: Convert to v4l2_ext_pix_format

Simplify Multi/Single planer API handling by converting to v4l2_ext_pix_format.

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Helen Koike <helen.koike@collabora.com>
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Changes in v6:
- Update with new format and buffer structs

Changes in v4:
- Update with new format and buffer structs
- Rebased on top of media/master (post 5.8-rc1)

Changes in v3:
- Rebased on top of media/master (post 5.4-rc1)

Changes in v2:
- New patch