SUNRPC: net/sunrpc/xdr.c: remove xdr_decode_string()

 This patch removes ths unused function xdr_decode_string().

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Acked-by: Neil Brown <neilb@suse.de>
Acked-by: Charles Lever <Charles.Lever@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>