systemd: fix efi dependency

systemd: fix efi dependency

Last version of systemd dpends now on pyelftools to build the efi support
but the required tool is the native ones and not the target.
The systemd-boot has the corrected dependencie so fix this in the main recipe.

| Program python3 (jinja2) found: YES (/build/tmp-lmp/work/corei7-64-lmp-linux/systemd/1_254-r0/recipe-sysroot-native/usr/bin/python3-native/python3) modules: jinja2
| Checking if "32bit build possible" : links: NO
| Program python3 (elftools) found: NO
|
| ../git/meson.build:2147:8: ERROR: Problem encountered: EFI bootloader support requires pyelftools.
|
| A full log can be found at /build/tmp-lmp/work/corei7-64-lmp-linux/systemd/1_254-r0/build/meson-logs/meson-log.txt

Signed-off-by: Jose Quaresma <jose.quaresma@foundries.io>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>