media: rp1: cfe: Add is_image_node()

The hardware supports streaming from memory (in addition to streaming
from the CSI-2 RX), but the driver does not support this at the moment.

There are multiple places in the driver which uses
is_image_output_node(), even if the "output" part is not relevant. Thus,
in a minor preparation for the possible support for streaming from
memory, and to make it more obvious that the pieces of code are not
about the "output", add is_image_node() which will return true for both
input and output video nodes.

While at it, reformat also the metadata related macros to fit inside 80
columns.

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