usb: gadget: serial: Limit write permissions to root

android compatibility test suite complains if others have write
permission. Hence, limit the file permissions to root.

Change-Id: I3f607b307b7ecb6c01180bc752681b02e6e54c7a
Signed-off-by: Vamsi Krishna <vskrishn@codeaurora.org>
1 file changed