Now that we've switched to packages in the model, rather than PN, it makes
sense to add an extra field to store the PN of the package.
This patch includes a convenience method to retrieve a list of selected PN's.
(Bitbake rev: cf79424592a81378de5edad11cf6c4f427c94bcc)
Signed-off-by: Joshua Lock <josh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>