Revert "iommu: make inclusion of arm/arm-smmu-v3 directory conditional"

Revert "iommu: make inclusion of arm/arm-smmu-v3 directory conditional"

This reverts commit e436576b0231542f6f233279f0972989232575a8.

That commit is very broken, and seems to have missed the fact that
CONFIG_ARM_SMMU_V3 is not just a yes-or-no thing, but also can be
modular.

So it caused build errors on arm64 allmodconfig setups:

  ERROR: modpost: "arm_smmu_make_cdtable_ste" [drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-test.ko] undefined!
  ERROR: modpost: "arm_smmu_make_s2_domain_ste" [drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-test.ko] undefined!
  ERROR: modpost: "arm_smmu_make_s1_cd" [drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-test.ko] undefined!
  ...

(and six more symbols just the same).

Link: https://lore.kernel.org/all/CAHk-=wh4qRwm7AQ8sBmQj7qECzgAhj4r73RtCDfmHo5SdcN0Jw@mail.gmail.com/
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Rolf Eike Beer <eb@emlix.com>
Cc: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>