nfsd: Remove unnecessary assignment in nfs4xdr.c

In nfsd4_encode_listxattrs(), the variable p is assigned to at one point
but this value is never used before p is reassigned. Fix this.

Addresses-Coverity: ("Unused value")
Signed-off-by: Alex Dewar <alex.dewar90@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfs4xdr.c

@@ -4859,7 +4859,7 @@ nfsd4_encode_listxattrs(struct nfsd4_compoundres *resp, __be32 nfserr,
 			goto out;
 		}
 
-		p = xdr_encode_opaque(p, sp, slen);
+		xdr_encode_opaque(p, sp, slen);
 
 		xdrleft -= xdrlen;
 		count++;