iommu/amd: Keep track of amd_iommu_irq_remap state

iommu/amd: Keep track of amd_iommu_irq_remap state

The amd_iommu_irq_remap variable is set to true in amd_iommu_prepare().
But if initialization fails it is not set to false. Fix that and
correctly keep track of whether irq remapping is enabled or not.

References: https://bugzilla.kernel.org/show_bug.cgi?id=212133
References: https://bugzilla.suse.com/show_bug.cgi?id=1183132
Fixes: 2f024562edcd ("iommu/amd: Stop irq_remapping_select() matching when remapping is disabled")
Cc: stable@vger.kernel.org # v5.11
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Link: https://lore.kernel.org/r/20210317091037.31374-4-joro@8bytes.org
Acked-by: Huang Rui <ray.huang@amd.com>