net: hns3: handle empty unknown interrupt

Since some MSI-X interrupt's status may be cleared by hardware,
so when the driver receives the interrupt, reading
HCLGE_VECTOR0_PF_OTHER_INT_STS_REG register will get an empty
unknown interrupt. For this case, the irq handler should enable
vector0 interrupt. This patch also use dev_info() instead of
dev_dbg() in the hclge_check_event_cause(), since this information
will be useful for normal usage.

Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: Peng Li <lipeng321@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>