package/opencv: define modules inter-dependencies

OpenCV allows to enable/disable the selection of modules (a.k.a.
opencv libraries). These modules depend one on the others; these
dependencies are already handled by the build-system (CMake).

However, the way we handled them in Buildroot was not really clean.
For each opencv module, there is a kconfig option, but we forced the
corresponding CMake config option without checking for the modules'
dependencies.

This patch replicates the modules' dependency relations in the
Config.in, so that the selection of the user will actually be built.

Signed-off-by: Samuel Martin <s.martin49@gmail.com>
Cc: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Cc: "Yann E. MORIN" <yann.morin.1998@free.fr>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>