vfio: platform: add the VFIO PLATFORM module to Kconfig

Enable building the VFIO PLATFORM driver that allows to use Linux platform
devices with VFIO.

Signed-off-by: Antonios Motakis <a.motakis@virtualopensystems.com>
Signed-off-by: Baptiste Reynal <b.reynal@virtualopensystems.com>
Reviewed-by: Eric Auger <eric.auger@linaro.org>
Tested-by: Eric Auger <eric.auger@linaro.org>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
diff --git a/drivers/vfio/Makefile b/drivers/vfio/Makefile
index 0b035b1..dadf0ca 100644
--- a/drivers/vfio/Makefile
+++ b/drivers/vfio/Makefile
@@ -3,3 +3,4 @@
 obj-$(CONFIG_VFIO_IOMMU_SPAPR_TCE) += vfio_iommu_spapr_tce.o
 obj-$(CONFIG_VFIO_SPAPR_EEH) += vfio_spapr_eeh.o
 obj-$(CONFIG_VFIO_PCI) += pci/
+obj-$(CONFIG_VFIO_PLATFORM) += platform/