Remove v4l2_scan_controls_enumerate_menu as appears unused and causes ioctl error.

See http://www.raspberrypi.org/forum/viewtopic.php?f=43&t=65026 for detail. Basically, this change copies the same procedure that v4l2-ctl uses in v4l2-ctl-common.cpp/print_qctrl (http://git.linuxtv.org/v4l-utils.git/tree/refs/heads/master:/utils/v4l2-ctl).

Original pull request attempted to just emulate the behavior of v4l2-ctl (https://github.com/Itseez/opencv/pull/2298)