systemd: add a hard dependency on udev=$EXTENDPKGV
If the systemd/sysvinit DISTRO_FEATURES are changed without wiping the package
feeds it's possible to build an image that pulls in mismatching versions of
systemd and udev. This leads to images that are broken and don't boot
correctly.
Prevent this by adding a version-locked dependency on udev in systemd so that
images that attempt to install mis-matching versions don't build.
Signed-off-by: Ross Burton <ross.burton@intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
