media: stm32-dcmi: add g/s_parm framerate support

Add g/s_parm framerate support by calling subdev
g/s_frame_interval ops.
This allows user to control sensor framerate by
calling ioctl G/S_PARM.

Signed-off-by: Hugues Fruchet <hugues.fruchet@st.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>