Kconfig already allows mpls to be built as module. Following patch
fixes Makefile to do same.
CC: Simon Horman <simon.horman@netronome.com> Signed-off-by: Pravin B Shelar <pshelar@nicira.com> Acked-by: Simon Horman <simon.horman@netronome.com> Signed-off-by: David S. Miller <davem@davemloft.net>