usb: Avoid incorrect memory leaks reported by kmemleak tool.

Certain memory allocations are not properly tracked by the kmemleak
tool, which causes it to incorrectly detect memory leaks. Notify the
tool by using kmemleak_not_leak() to ignore the memory allocation
so that incorrect leak reports are avoided.

CRs-Fixed: 612944
Change-Id: Ia15d94bb140f415a25d5b7e6996d3b985f33b28b
Signed-off-by: Saket Saurabh <ssaurabh@codeaurora.org>