[PATCH] USBATM: remove no-longer needed #include

We #include <linux/netdevice.h> only because <linux/etherdevice.h>
needed it, but didn't #include it itself.  But that's been fixed now.

Signed-off-by: Duncan Sands <baldrick@free.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>