media: ov6650: Fix missing frame interval enumeration support

According to v4l2-compliance utility, a video device which supports
V4L2_CAP_TIMEPERFRAME via .vidioc_s_parm() operation should also
support .vidioc_enum_frameintervals().  If the former is implemented
via a call to v4l2_s_parm_cap() which in turn calls a subdevice
.s_frame_interval() pad operation, the video device may want to
implement the latter by passing frame interval enumeration requests to
the subdevice .enum_frame_intervals() video operation.  If that
operation is not supported by the subdevice and failure is returned by
the video device, the compliance test issues a warning.

Implement the missing pad operation.  Enumerate frame intervals
possible to be set via pixel clock adjustment, as implemented by
.s_frame_interval(), but not exceeding a reasonable maximum of 1
second.

[Sakari Ailus: Rebased on mbus config pad op patches]

Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>