net: sctp: trivial: add uapi/linux/sctp.h into maintainers

After this file has moved to the uapi section, we also need to update
this in the maintainers file.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Vlad Yasevich <vyasevich@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

MAINTAINERS

@@ -7216,6 +7216,7 @@ W:	http://lksctp.sourceforge.net
 S:	Maintained
 F:	Documentation/networking/sctp.txt
 F:	include/linux/sctp.h
+F:	include/uapi/linux/sctp.h
 F:	include/net/sctp/
 F:	net/sctp/