i40e: store msg_enable in the right size

The kernel returns a u32 for netif_msg_init, and we were storing
it in a u16.  Fix the width of the datatype.

Change-ID: I4b23326e5707c91cd59325c5a1ccb2ba7a3974fc
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>