USB: Trival cleanup in MSM drivers

Changes:
1. strncpy() to strlcpy()
2. sprintf() to snprintf()
3. Add buffer size in sscanf()
4. Fix the accessing of NULL pointers

Change-Id: I27c05d21a6551026764b0d3b2dbd8756a5992b20
Signed-off-by: Rajkumar Raghupathy <raghup@codeaurora.org>