iommu/amd: Fix panic accessing amd_iommu_enable_faulting

iommu/amd: Fix panic accessing amd_iommu_enable_faulting

This fixes a bug introduced by commit d74169ceb0d2 ("iommu/vt-d: Allocate
DMAR fault interrupts locally").  The panic happens when
amd_iommu_enable_faulting is called from CPUHP_AP_ONLINE_DYN context.

Fixes: d74169ceb0d2 ("iommu/vt-d: Allocate DMAR fault interrupts locally")
Signed-off-by: Dimitri Sivanich <sivanich@hpe.com>
Tested-by: Yi Zhang <yi.zhang@redhat.com>
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
Link: https://lore.kernel.org/r/ZljHE/R4KLzGU6vx@hpe.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>