Only build ivshmem when CONFIG_PCI && CONFIG_KVM

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>

Makefile.target

diff --git a/Makefile.target b/Makefile.target
index ddb0931..04e20dd 100644
--- a/Makefile.target
+++ b/Makefile.target
@@ -209,7 +209,13 @@
 obj-$(CONFIG_XEN) += xen_machine_pv.o xen_domainbuild.o
 
 # Inter-VM PCI shared memory
-obj-$(CONFIG_KVM) += ivshmem.o
+CONFIG_IVSHMEM =
+ifeq ($(CONFIG_KVM), y)
+  ifeq ($(CONFIG_PCI), y)
+    CONFIG_IVSHMEM = y
+  endif
+endif
+obj-$(CONFIG_IVSHMEM) += ivshmem.o
 
 # Hardware support
 obj-i386-y += vga.o