FROMLIST: Revert "iommu/arm-smmu: Make arm-smmu explicitly non-modular"

This reverts commit addb672f.

Let's get the SMMU driver building as a module, which means putting
back some dead code that we used to carry.

Signed-off-by: Will Deacon <will@kernel.org>
Bug: 140290589
Link: https://lore.kernel.org/lkml/20191121114918.2293-9-will@kernel.org/


Signed-off-by: Will Deacon <willdeacon@google.com>
Change-Id: I9779ffa7befa8535a0d7196ef5f728e40ae7d7f7