iavf: Log info when VF is entering and leaving Allmulti mode

Add log when VF is entering and leaving Allmulti mode.
The change of VF state is visible in dmesg now.
Without this commit, entering and leaving Allmulti mode
is not logged in dmesg.

Signed-off-by: Grzegorz Szczurek <grzegorzx.szczurek@intel.com>
Tested-by: George Kuruvinakunnel <george.kuruvinakunnel@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>