net/enetc: Fix wrong return value in enetc_psfp_parse_clsflower()

In the case of invalid rule, a positive value EINVAL is returned here.
I think this is a typo error. It is necessary to return an error value.

Cc: Po Liu <Po.Liu@nxp.com>
Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>