[media] v4l: rename v4l2_format_sdr to v4l2_sdr_format

Rename v4l2_format_sdr to v4l2_sdr_format in order to keep it in
line with other formats.

Reported-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>