classes/package: set SUMMARY in do_split_packages()
do_split_packages() is commonly used to split out plugin/module packages
dynamically within recipes. If it doesn't set SUMMARY for each of these
packages then they get a generic SUMMARY from the recipe, which isn't
particularly useful; so add a parameter to set this and default it from
the current description parameter (it ought to have been the other way
around, but the description parameter is what we currently have in use
by all recipes that use this function.)
Fixes [YOCTO #5406].
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
