net: hns: Fix some kernel-doc warnings in hns_dsaf_xgmac.c

Fixes the following W=1 kernel build warning(s):

drivers/net/ethernet/hisilicon/hns/hns_dsaf_xgmac.c:137: warning: Excess function parameter 'drv' description in 'hns_xgmac_enable'
drivers/net/ethernet/hisilicon/hns/hns_dsaf_xgmac.c:497: warning: Excess function parameter 'cmd' description in 'hns_xgmac_get_regs'

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wang Hai <wanghai38@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>