systemd: mount the EFI variable filesystem

systemd: mount the EFI variable filesystem

Add efivarfs to the mount_table in mount-setup.c, so the EFI variable
filesystem will be mounted when systemd executed.

The EFI variable filesystem will merge in v3.7 or v3.8 linux kernel.

Cc: Kay Sievers <kay@vrfy.org>
Cc: Lennart Poettering <lennart@poettering.net>
Cc: Mantas Mikulėnas <grawity@gmail.com>
Cc: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
Cc: Matt Fleming <matt.fleming@intel.com>
Cc: Jeremy Kerr <jeremy.kerr@canonical.com>
Cc: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Lee, Chun-Yi <jlee@suse.com>