NFSD: Remove unused results in nfsd4_encode_pathname4()

Clean up. The result of "*p++" is saved, but is not used before it
is overwritten. The result of xdr_encode_opaque() is saved each
time through the loop but is never used.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>