net: hns3: keep MAC pause mode when multiple TCs are enabled

Bellow HNAE3_DEVICE_VERSION_V3, MAC pause mode just support one
TC, when enabled multiple TCs, force enable PFC mode.

HNAE3_DEVICE_VERSION_V3 can support MAC pause mode on multiple
TCs, so when enable multiple TCs, just keep MAC pause mode,
and enable PFC mode just according to the user settings.

Signed-off-by: Yonglong Liu <liuyonglong@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>