USB: Trivial cleanup in MSM drivers

This patch does the following cleanup:

1. Use strncpy() instead of strcpy()
2. Add NULL reference checks
3. Remove unnecessary NULL checks
3. Fix accessing dangling pointers
4. Pass target's string length as length argument to memcmp().

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

Conflicts:

	drivers/usb/gadget/android.c