ocf: switch MODULE_LICENSE from BSD to "Dual BSD/GPL" to make the kernel recognize modules as GPL-compatible

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt@37769 3c298f89-4303-0410-b956-a3cf2f4a3e73