ENGR00211376 Capture: ov5640_mipi: the QVGA is brighter

ENGR00211376 Capture: ov5640_mipi: the QVGA is brighter

change ov5640_init_mode sequence according to ov's suggestion

ov5640 support two method of size switching, scaling and subsampling
exposure calculation when change size between scaling and subsampling
- scaling: image size bigger than 1280*960
- subsampling: image size smaller than 1280*960

This patch changes the sequence of ov5640_init_mode()
1. setting mipi csi2 (no change).
2. check mode
- if it is in INIT_MODE, go throught initial procedure
- if sensor changes between scaling and subsampling,
  go through exposure calcualtion
- otherwise, configure mode directly.
3. other procedures keep the same.

Signed-off-by: Sheng Nan <b38800@freescale.com>