FROMLIST: drivers/iommu: Export core IOMMU API symbols to permit modular drivers

Building IOMMU drivers as modules requires that the core IOMMU API
symbols are exported as GPL symbols.

Signed-off-by: Will Deacon <will@kernel.org>
Bug: 140290589
Link: https://lore.kernel.org/lkml/20191121114918.2293-2-will@kernel.org/


Signed-off-by: Will Deacon <willdeacon@google.com>
Change-Id: Ic1b3b5e6e92c5852af1e3473dd230c506b8d7865