iommu/mediatek: Fix MTK_IOMMU dependencies

If NO_DMA=y (e.g. Sun-3 all{mod,yes}-config):

    drivers/iommu/dma-iommu.o: In function `iommu_dma_mmap':
    dma-iommu.c:(.text+0x836): undefined reference to `dma_pgprot'

IOMMU_DMA must not be selected, unless HAS_DMA=y.

Hence fix this by making MTK_IOMMU depend on HAS_DMA.
While at it, remove the dependency on ARM || ARM64, as that is already
implied by the dependency on ARCH_MEDIATEK.

Fixes: e93a1695d7 ("iommu: Enable compile testing for some of drivers")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/r/20200410143047.19691-1-geert@linux-m68k.org
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/Kconfig

@@ -457,7 +457,7 @@ config S390_AP_IOMMU
 
 config MTK_IOMMU
 	bool "MTK IOMMU Support"
-	depends on ARM || ARM64 || COMPILE_TEST
+	depends on HAS_DMA
 	depends on ARCH_MEDIATEK || COMPILE_TEST
 	select ARM_DMA_USE_IOMMU
 	select IOMMU_API