remoteproc: st: add virtio communication support

This patch provides virtio communication support based on mailbox
for ST co-processors.

Signed-off-by: Loic Pallardy <loic.pallardy@st.com>
Signed-off-by: Ludovic Barre <ludovic.barre@st.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
diff --git a/drivers/remoteproc/Kconfig b/drivers/remoteproc/Kconfig
index 402de70..65f86bc 100644
--- a/drivers/remoteproc/Kconfig
+++ b/drivers/remoteproc/Kconfig
@@ -118,6 +118,9 @@
 	tristate "ST remoteproc support"
 	depends on ARCH_STI
 	depends on REMOTEPROC
+	select MAILBOX
+	select STI_MBOX
+	select RPMSG_VIRTIO
 	help
 	  Say y here to support ST's adjunct processors via the remote
 	  processor framework.