leaking_addresses: add to exclude files/paths list

There are a couple more files that cause the script to stall.

/sys/firmware/devicetree and its symlink /proc/device-tree, reported by
Michael Ellerman.

usbmon should be skipped were ever it appears. Reported by Kees Cook

Add files to be excluded from parsing.

Signed-off-by: Tobin C. Harding <me@tobin.cc>