Convert fxp(4) to use the driver API.

Submitted by:	Anuranjan Shukla <anshukla@juniper.net>
Obtained from:	Juniper Networks, Inc.
Convert em(4) to use the driver API.

Submitted by:   Anuranjan Shukla <anshukla@juniper.net>
Obtained from:  Juniper Networks, Inc.
Convert bxe(4) to use the driver API.

Submitted by:   Sreekanth Rupavatharam <rupavath@juniper.net>
Obtained from:  Juniper Networks, Inc.