greybus: camera: Add bpp to Greybus Format description

Add the bytes per pixel value to the structure describing a Greybus
Protocol Image Format.
The bpp information will be used to compute the length in bytes of a
line of pixel data

Signed-off-by: Jacopo Mondi <jacopo.mondi@linaro.org>
Reviewed-by: Gjorgji Rosikopulos <grosikopulos@mm-sol.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>