[media] omap3isp: preview: Merge configuration and feature bits

The preview engine parameters are referenced by a value suitable for
being used in a bitmask. Two macros named OMAP3ISP_PREV_* and PREV_* are
declared for each parameter and are used interchangeably. Remove the
private macro.

Replace the configuration bit field in the parameter update attributes
structure with a boolean that indicates whether the parameter can be
updated through the preview engine configuration ioctl.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>