intel-iommu: Apply BIOS sanity checks for interrupt remapping too.

The BIOS errors where an IOMMU is reported either at zero or a bogus
address are causing problems even when the IOMMU is disabled -- because
interrupt remapping uses the same hardware. Ensure that the checks get
applied for the interrupt remapping initialisation too.

Cc: stable@kernel.org
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>