[yocto] source added to -dbg pkg

[Kyle Farnsworth]

> I would like to NOT put the source code within the ${PN}-dbg pkg and
> keep it separate from my symbol binaries in that pkg.  Is there a way to
> either turn off the collection of the source or allow me to put it in a
> different pkg.  It could be useful to have some cases but not in all.
I just figured out I could move it to it's own pkg using this:
PACKAGES =+ " ${PN}-src "
FILES_${PN}-src = "${DEBUGFILESDIRECTORY-dbg}"