usb: gadget: Avoid exposing kernel addresses

Usage of %p exposes the kernel addresses, an easy target to
kernel write vulnerabilities. With this patch currently
%pK prints only Zeros as address. If you need actual address
echo 0 > /proc/sys/kernel/kptr_restrict

Change-Id: Ie998f020f332b0992f38567d703f3ff7df0d188e
Signed-off-by: Dennis Cagle <d-cagle@codeaurora.org>