libnl-tiny: ensure compatibility to libnl version 3 and higher

To be prepared to support keepalived 1.2.10 and higher we need libnl3 or
higher. The attached patch
add some defines so that it can be build be libnl-tiny.
Patch by Thomas Heil

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

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@39991 3c298f89-4303-0410-b956-a3cf2f4a3e73