media: i2c: Update HTS values in ov8865

The HTS values for some of the modes in the ov8865 driver are a bit
unusual, coming in lower than the output_size_x is set to. It seems
like they might be calculated to fit the desired framerate into a
configuration with just two data lanes. To bring this more in line
with expected behaviour, raise the HTS values above the output_size_x.

The corollary of that change is that the hardcoded frame intervals
against the modes no longer make sense, so remove those entirely.
Update the .g/s_frame_interval() callbacks to calculate the frame
interval based on the current mode and the vblank and hblank settings.

The implementation of the .enum_frame_interval() callback is no longer
suitable since the possible frame rate is now a continuous range depending
on the vblank control setting, so remove that callback entirely.

Signed-off-by: Daniel Scally <djrscally@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>