x86: Remove the calgary IOMMU driver

The calgary IOMMU was only used on high-end IBM systems in the early
x86_64 age and has no known users left.  Remove it to avoid having to
touch it for pending changes to the DMA API.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191113071836.21041-2-hch@lst.de