media: coda: implement ENUM_FRAMEINTERVALS

v4l2-compliance complains about S_PARM being supported, but not
ENUM_FRAMEINTERVALS.
Report a continuous frame interval even though the hardware only
supports 16-bit numerator and denominator, with min/max values
that can be programmed into the mailbox registers.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Hans Verkuil <hansverk@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>