The ivshmem depends on PCI and KVM, not only KVM. Reflect this
in the Makefile, so we don't get build errors on s390x.

Signed-off-by: Alexander Graf <agraf@suse.de>
CC: Cam Macdonell <cam@cs.ualberta.ca>
CC: Juan Quintela <quintela@redhat.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>