usb: gadget: u_ether: Remove duplicated include in u_ether.c

Fix following includecheck warning:
./drivers/usb/gadget/function/u_ether.c: linux/etherdevice.h is included
more than once.

Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Link: https://lore.kernel.org/r/20220623010808.9816-1-yang.lee@linux.alibaba.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>