usb: android: Fix bug in ECM bind

The gether_setup_name() function returns the error as pointer. The
current code is checking the return value against NULL and failing
ECM bind for the success case. Use IS_ERR() to check the return
value.

Change-Id: I32d546a92fd91a6c63ea73df33ae0ee5ef702243
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>