media: ccs-pll: Add a flag for even PLL multipliers

Some devices (not entirely CCS compliant) only support even PLL
multipliers. Add support for this through a PLL flag.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>