selftests: media_tests add a new video device test

Add a new video device test that opens user specified Video Device and
calls video ioctls in a loop once every 10 seconds.

This test is intended for testing device removal and driver unbind while
an ioctl is active. Clean device removal and driver unbind is expected
without any use-after-free and panics.

Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>