Add #define's for the "AEC MANUAL" (0x3503) register and its
values/flags. Use those in the registers single usage within the
`common_regs` struct.
All values are based on the OV9281 datasheet v1.01 (09.18.2015).
Signed-off-by: Richard Leitner <richard.leitner@linux.dev> Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com> Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com> Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>