qiprog: Add test to check for buffering bugs in device or driver

These tests stress set_address/readn combinations in a number of ways which
expose seemingly innocent bugs. More details in comments.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
usb_master: Fix trivial error to allow compiling with clang

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>