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/Kconfig b/drivers/vfio/Kconfig
index 14e27ab..d5322a4 100644
--- a/drivers/vfio/Kconfig
+++ b/drivers/vfio/Kconfig
@@ -27,3 +27,4 @@
 	  If you don't know what to do here, say N.
 
 source "drivers/vfio/pci/Kconfig"
+source "drivers/vfio/platform/Kconfig"