build-sys: restrict vmcoreinfo to fw_cfg+dma capable targets

vmcoreinfo is built for all targets. However, it requires fw_cfg with
DMA operations support (write operation). Restrict vmcoreinfo exposure
to architectures that are supporting FW_CFG_DMA, that is arm-virt and
x86 only atm.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Daniel Henrique Barboza <danielhb@linux.vnet.ibm.com>
Tested-by: Daniel Henrique Barboza <danielhb@linux.vnet.ibm.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

default-configs/arm-softmmu.mak

@@ -130,3 +130,5 @@ CONFIG_SMBIOS=y
 CONFIG_ASPEED_SOC=y
 CONFIG_GPIO_KEY=y
 CONFIG_MSF2=y
+
+CONFIG_FW_CFG_DMA=y

default-configs/i386-softmmu.mak

@@ -60,3 +60,4 @@ CONFIG_SMBIOS=y
 CONFIG_HYPERV_TESTDEV=$(CONFIG_KVM)
 CONFIG_PXB=y
 CONFIG_ACPI_VMGENID=y
+CONFIG_FW_CFG_DMA=y

default-configs/x86_64-softmmu.mak

@@ -60,3 +60,4 @@ CONFIG_SMBIOS=y
 CONFIG_HYPERV_TESTDEV=$(CONFIG_KVM)
 CONFIG_PXB=y
 CONFIG_ACPI_VMGENID=y
+CONFIG_FW_CFG_DMA=y

hw/misc/Makefile.objs

@@ -9,7 +9,7 @@ common-obj-$(CONFIG_PCI_TESTDEV) += pci-testdev.o
 common-obj-$(CONFIG_EDU) += edu.o
 
 common-obj-y += unimp.o
-common-obj-y += vmcoreinfo.o
+common-obj-$(CONFIG_FW_CFG_DMA) += vmcoreinfo.o
 
 obj-$(CONFIG_VMPORT) += vmport.o