NFSD: fix compile warning without CONFIG_NFSD_V3

Without CONFIG_NFSD_V3, compile will get warning as,

fs/nfsd/nfssvc.c: In function 'nfsd_svc':
>> fs/nfsd/nfssvc.c:246:60: warning: array subscript is above array bounds [-Warray-bounds]
        return (nfsd_versions[2] != NULL) || (nfsd_versions[3] != NULL);
                                                               ^

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfssvc.c

@@ -243,7 +243,11 @@ static void nfsd_shutdown_generic(void)
 
 static bool nfsd_needs_lockd(void)
 {
+#if defined(CONFIG_NFSD_V3)
 	return (nfsd_versions[2] != NULL) || (nfsd_versions[3] != NULL);
+#else
+	return (nfsd_versions[2] != NULL);
+#endif
 }
 
 static int nfsd_startup_net(int nrservs, struct net *net)