package_deb: Split do_package_write_deb into two functions
This prepares the way to parallelise deb generation and splits the iteration
over packages and the package generation into separate functions. Whitespace
indentation is unchanged deliberately and is fixed in a followup patch. There
should be no functional change.
Some checks on variables are removed as they were pointless when you looked
at the code.
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
