package/nvme: add systemd optional dependency

systemd is an optional dependency (enabled by default) since version
1.10 and
https://github.com/linux-nvme/nvme-cli/commit/48c10dbfaf00777170e209db20f7d07e47f7a983

Fixes:
 - http://autobuild.buildroot.org/results/8d14a5702aa1ffe3f036d1e1505e9596e3d4d466



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>