The Calgary IOMMU driver has been removed in

  90dc392f ("x86: Remove the calgary IOMMU driver")

Clean up stale docs that refer to it.
Signed-off-by: Hubert Jasudowicz <hubert.jasudowicz@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/1bd2b57dd1db53df09e520b8170ff61418805de4.1623274832.git.hubert.jasudowicz@gmail.com