iommu: shmobile: Enable driver compilation with COMPILE_TEST

This helps increasing build testing coverage.

The driver doesn't compile on non-ARM platforms due to usage of the ARM
DMA IOMMU API, restrict compilation to ARM.

Cc: Joerg Roedel <joro@8bytes.org>
Cc: iommu@lists.linux-foundation.org
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Joerg Roedel <joro@8bytes.org>

drivers/iommu/Kconfig

@@ -207,6 +207,7 @@ config SHMOBILE_IOMMU
 	bool "IOMMU for Renesas IPMMU/IPMMUI"
 	default n
 	depends on ARM
+	depends on SH_MOBILE || COMPILE_TEST
 	select IOMMU_API
 	select ARM_DMA_USE_IOMMU
 	select SHMOBILE_IPMMU