MAINTAINERS: Update amd-iommu F: patterns

Commit 29b68415 ("x86: amd_iommu: move to drivers/iommu/")
moved the files, update the patterns.

CC: Ohad Ben-Cohen <ohad@wizery.com>
CC: Joerg Roedel <joerg.roedel@amd.com>

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>