net: hns3: increase the max time for IMP handle command

It may need more time for IMP handle some command, such as reset.
This patch enlarges the max time for cmd timeout.

Driver will check the IMP result every us, it may break through the
loop when get the right result. So not all command need the max time.

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