iavf: Move commands processing to the separate function

Move the commands processing outside the watchdog_task()
function. This reduce length and complexity of the function
which is mainly designed to process the watchdog state machine.

Signed-off-by: Jakub Pawlak <jakub.pawlak@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>