opencv: Add missing dependencies

opencv-3.1+gitAUTOINC+92387b1ef8: libopencv-videoio rdepends on
libgphotoport, but it isn't a build dependency, missing libgphoto2 in
DEPENDS or PACKAGECONFIG? [build-deps]
opencv-3.1+gitAUTOINC+92387b1ef8: libopencv-videoio rdepends on
libgphoto2, but it isn't a build dependency, missing libgphoto2 in
DEPENDS or PACKAGECONFIG? [build-deps]
opencv-3.1+gitAUTOINC+92387b1ef8: libopencv-dnn rdepends on protobuf,
but it isn't a build dependency, missing protobuf in DEPENDS or
PACKAGECONFIG? [build-deps]

Credit-to: Martin Jansa <martin.jansa@gmail.com>
Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>