Revert "opencv: cleanup depends and comments"

This reverts commit 5f7cbb26.

Buildroot policy is to keep the dependencies / comments for sub options in
case the package in the future no longer has those dependencies.

See http://lists.busybox.net/pipermail/buildroot/2014-February/088523.html


for details.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>