fm10k: implement reset_notify handler for PCIe FLR events

When a function level PCI reset is triggered using sysfs, it calls the
driver's .reset_notify error handler. Implement a handler based on the
now split fm10k_prepare_for_reset and fm10k_handle_reset functions, so
that we fully reset the driver when the PCI function level reset occurs.
This also ensures the reset is handled in a clean way by first disabling
all the driver bits first and then restoring them after the function
reset. Previously the stack simply performed a blind function reset and
our driver didn't take any part in the process.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Krishneil Singh <Krishneil.k.singh@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>