recipetool/devtool: Further SPDX identifier cleanups

recipetool/devtool: Further SPDX identifier cleanups

Some of these are hard to know what to do with since the original source
files for the checksum aren't present. The safe option is to use "-only"
as often the main license is ambiguous and the source files themselves
determine the "or-later" possibility. The "-only" option therefore is
realistically what we need to use in this code.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>