systemd: Use PACKAGE_BEFORE_PN, not =+

By using PACKAGE_BEFORE_PN rather than =+ it's clearer how we expect the
package ordering to work. It also avoids the possibilty that dev/dbg/etc.
artefacts attempt to package as part of these packages.

(From OE-Core rev: fb64a50c3ab385d5bfd33dd669b6148e43b43770)

Signed-off-by: Alex Kiernan <alex.kiernan@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-core/systemd/systemd_244.3.bb

@@ -307,7 +307,7 @@ python populate_packages_prepend (){
 }
 PACKAGES_DYNAMIC += "^lib(udev|systemd|nss).*"
 
-PACKAGES =+ "\
+PACKAGE_BEFORE_PN = "\
     ${PN}-gui \
     ${PN}-vconsole-setup \
     ${PN}-initramfs \
@@ -321,6 +321,8 @@ PACKAGES =+ "\
     ${PN}-journal-upload \
     ${PN}-journal-remote \
     ${PN}-extra-utils \
+    udev \
+    udev-hwdb \
 "
 
 SUMMARY_${PN}-container = "Tools for containers and VMs"
@@ -580,8 +582,6 @@ INSANE_SKIP_${PN} += "dev-so libdir"
 INSANE_SKIP_${PN}-dbg += "libdir"
 INSANE_SKIP_${PN}-doc += " libdir"
 
-PACKAGES =+ "udev udev-hwdb"
-
 RPROVIDES_udev = "hotplug"
 
 RDEPENDS_udev-hwdb += "udev"