media: imx: utils: Rename pixel format selection enumeration

After the introduction of the CS_SEL_BAYER flag, the "codespace"
pixel format selection enumeration wording no longer makes sense
(and even before, when selecting between YUV or RGB formats,
"codespace" was a misuse of the term).

Rename

- 'enum codespace_sel' to 'enum imx_pixfmt_sel'
- CS_SEL_* to PIXFMT_SEL_*
- local vars named cs_sel to fmt_sel or just sel

No functional changes.

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>