afs, rxrpc: Update the MAINTAINERS file

Update the MAINTAINERS file for AFS and AF_RXRPC to include a website
pointer.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

MAINTAINERS

@@ -540,6 +540,7 @@ S:	Supported
 F:	fs/afs/
 F:	include/net/af_rxrpc.h
 F:	net/rxrpc/af_rxrpc.c
+W:	https://www.infradead.org/~dhowells/kafs/
 
 AGPGART DRIVER
 M:	David Airlie <airlied@linux.ie>