convert license headers to SPDX

Includes license review of 3rd-party files, adding missing upstream
headers, and moving the UNSW OZPLB license into its own file rather
than replicating it in the header.

common-tool: Moved some tools to misc

Moved some miscellaneous tools from common-tool to the misc
folder. Common-tool mainly consists of Kbuild items which
is no longer supported.