media: rp1: cfe: Fix default meta format's field

Set default meta format's field to V4L2_FIELD_NONE, instead of zeroing
it which indicates V4L2_FIELD_ANY. Metadata doesn't have fields, so NONE
makes sense, and furthermore the default v4l2 link validation will check
for matching fields, or that the sink field is NONE.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>