i40e: reset the invalid msg counter in vf when a valid msg is received

When the number of invalid messages from a VF is exceeded, the VF
will be disabled, due to the invalid messages.  This happens if
other VF drivers (like DPDK) send a message through the driver's
mailbox (aka virtchannel) interface, but the message is not
supported by the i40e pf driver, such as CONFIG_PROMISCUOUS_MODE.

This patch changes the num_invalid_msgs in struct i40e_vf to record
the continuous invalid msgs, and it will be reset when a valid msg
is received.

Change-ID: Iaec42fd3dcdd281476b3518be23261dd46fc3718
Signed-off-by: Jingjing Wu <jingjing.wu@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>