ARM: multi_v7_defconfig: Select RPMSG_VIRTIO as module

The RPMSG_VIRTIO is now user selectable option so we explicitly
select it in multi_v7_defconfig. Till now RPMSG_VIRTIO was
selected by ST_REMOTEPROC=m in multi_v7_defconfig.
Signed-off-by: Anup Patel <anup@brainfault.org>
Acked-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/arm/configs/multi_v7_defconfig

@@ -855,6 +855,7 @@ CONFIG_TEGRA_IOMMU_GART=y
 CONFIG_TEGRA_IOMMU_SMMU=y
 CONFIG_REMOTEPROC=m
 CONFIG_ST_REMOTEPROC=m
+CONFIG_RPMSG_VIRTIO=m
 CONFIG_PM_DEVFREQ=y
 CONFIG_ARM_TEGRA_DEVFREQ=m
 CONFIG_MEMORY=y