NFSD: Cleanup unneeded including net/ipv6.h

Commit 49b28684 ("nfsd: Remove deprecated nfsctl system call and
related code") removed the only use of ipv6_addr_set_v4mapped(), so
net/ipv6.h is unneeded now.
Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/export.c

@@ -17,8 +17,6 @@
 #include <linux/exportfs.h>
 #include <linux/sunrpc/svc_xprt.h>
 
-#include <net/ipv6.h>
-
 #include "nfsd.h"
 #include "nfsfh.h"
 #include "netns.h"