net/iavf: add watchdog for VF FLR

net/iavf: add watchdog for VF FLR

Add watchdog to iAVF PMD which support monitoring the VFLR register. If
the device is not already in reset then if a VF reset in progress is
detected then notify user through callback and set into reset state.
If the device is already in reset then poll for completion of reset.

The watchdog is disabled by default, to enable it set
IAVF_DEV_WATCHDOG_PERIOD to a non zero value (microseconds)

Signed-off-by: Declan Doherty <declan.doherty@intel.com>
Signed-off-by: Radu Nicolau <radu.nicolau@intel.com>
Acked-by: Jingjing Wu <jingjing.wu@intel.com>