V4L/DVB (10093): soc-camera: add new bus width and signal polarity flags

In preparation for i.MX31 camera host driver add flags for 4 and 15 bit bus
widths and for data lines polarity inversion.

Signed-off-by: Guennadi Liakhovetski <lg@denx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>