iommu/mediatek-v1: Support COMPILE_TEST

Add COMPILE_TEST support to Mediatek v1 so I have less chance of
breaking it again in future. This just needs the ARM dma-iommu API
stubbing out for now.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/a8d7c0b4393b360ce556f5f15e229d1e2fe73c83.1741702556.git.robin.murphy@arm.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Author: rmurphy-arm

drivers/iommu/Kconfig

@@ -482,8 +482,7 @@ config MTK_IOMMU
 
 config MTK_IOMMU_V1
 	tristate "MediaTek IOMMU Version 1 (M4U gen1) Support"
-	depends on ARM
-	depends on ARCH_MEDIATEK || COMPILE_TEST
+	depends on (ARCH_MEDIATEK && ARM) || COMPILE_TEST
 	select ARM_DMA_USE_IOMMU
 	select IOMMU_API
 	select MEMORY

drivers/iommu/mtk_iommu_v1.c

@@ -27,11 +27,20 @@
 #include <linux/spinlock.h>
 #include <linux/string_choices.h>
 #include <asm/barrier.h>
-#include <asm/dma-iommu.h>
 #include <dt-bindings/memory/mtk-memory-port.h>
 #include <dt-bindings/memory/mt2701-larb-port.h>
 #include <soc/mediatek/smi.h>
 
+#if defined(CONFIG_ARM)
+#include <asm/dma-iommu.h>
+#else
+#define arm_iommu_create_mapping(...) NULL
+#define arm_iommu_attach_device(...)	-ENODEV
+struct dma_iommu_mapping {
+	struct iommu_domain *domain;
+};
+#endif
+
 #define REG_MMU_PT_BASE_ADDR			0x000
 
 #define F_ALL_INVLD				0x2