USB: android: Avoid typecasting sysfs buffer

Avoid typecasting sysfs buffer from const char * to char * for the
sake of passing it to strim().  Copy sysfs buffer to internal buffer
and call strim on it.

Change-Id: I7d23ce6fcd0b5e6b832ecbb10e0f07d27000f905
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>