package/opencv: define modules inter-dependencies

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.
For further details about the issues this situation was causing, refer
to this discussion [1].

This patch replicates the modules' dependency relations in the
Config.in, so that the selection of the user will actually be built.
This changes completes this work [2].

[1] http://lists.busybox.net/pipermail/buildroot/2016-April/159017.html
[2] https://git.buildroot.org/buildroot/commit/?id=3bd5025038a9ecfb2c19a2450a68ae3b0888b440

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>
Cc: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>