iommu: make inclusion of riscv directory conditional

Nothing in there is active if CONFIG_RISCV_IOMMU is not enabled, so the whole
directory can depend on that switch as well.

Fixes: 5c0ebbd ("iommu/riscv: Add RISC-V IOMMU platform device driver")
Signed-off-by: Rolf Eike Beer <eb@emlix.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/2235451.Icojqenx9y@devpool92.emlix.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Author: DerDakon

drivers/iommu/Makefile

@@ -1,7 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0
-obj-y += arm/ iommufd/ riscv/
+obj-y += arm/ iommufd/
 obj-$(CONFIG_AMD_IOMMU) += amd/
 obj-$(CONFIG_INTEL_IOMMU) += intel/
+obj-$(CONFIG_RISCV_IOMMU) += riscv/
 obj-$(CONFIG_IOMMU_API) += iommu.o
 obj-$(CONFIG_IOMMU_SUPPORT) += iommu-pages.o
 obj-$(CONFIG_IOMMU_API) += iommu-traces.o

drivers/iommu/riscv/Makefile

@@ -1,3 +1,3 @@
 # SPDX-License-Identifier: GPL-2.0-only
-obj-$(CONFIG_RISCV_IOMMU) += iommu.o iommu-platform.o
+obj-y += iommu.o iommu-platform.o
 obj-$(CONFIG_RISCV_IOMMU_PCI) += iommu-pci.o