media: ov5640: Drop dead code using frame_interval

The ov5640_update_pixel_rate() function handles the parallel and MIPI
CSI-2 cases separately.

When running on a parallel setup the V4L2_CID_PIXEL_RATE value is
calculated at the beginning of the function using the values configured
with the frame_interval operations, and then the function immediately
returns.

The remaining of the function handles the MIPI CSI-2 configuration and
should not use the 'current_fr' and 'def_fps' fields as those are only
relevant for parallel mode.

Drop a small section of dead code that updates vblank using
frame_interval on a MIPI CSI-2 setup.

Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>