net: hns3: Add *Asserting Reset* mailbox message & handling in VF

Reset Asserting message is forwarded by PF to inform VF about
the hardware reset which is about to happen. This might be due
to the earlier VF reset request received by the PF or because PF
for any reason decides to undergo reset. This message results in
VF to go in pending state in which it polls the hardware to
complete the reset and then further resets/tears its own stack.

Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>