USB: Fix multiple issues found by static analysis tool

when static analysis tool is run, it could give defects in the code
like uninitialized variable, checking unsigned variable less than zero,
accessing pointers before checking whether it is NULL or not. Hence
fix all those errors found by static analysis tool.

CRs-Fixed: 550211
Change-Id: I591cec57d8cc1f26be611598f43d1f000f41fb2f
Signed-off-by: Vijayavardhan Vennapusa <vvreddy@codeaurora.org>