amd_iommu: do not dereference a NULL pointer address.

under low memory conditions, alloc_pte() may return a NULL pointer.
iommu_map_page() does not check it and will panic the system.

Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
iommu/amd: Fix devid mapping for ivrs_ioapic override

When the device id for an IOAPIC is overridden on the kernel
command line, the iommu driver has to make sure it sets up a
DTE for this device id.

Reported-by: Su Friendy <friendy.su@sony.com.cn>
Signed-off-by: Joerg Roedel <jroedel@suse.de>