[media] ad9389b: change initial register configuration in ad9389b_setup()

- register 0x17: CSC scaling factor was set to +/- 2.0. This register
  is set by ad9389b_csc_conversion_mode() to the right value.
- register 0x3b: bits for pixel repetition and CSC was set to zero,
  but that is the default value.

Signed-off-by: Mats Randgaard <matrandg@cisco.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>