iommu/vt-d: Remove unused PASID_DISABLED

The macro is unused after commit 00ecd540

 so it can be removed.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Fixes: 00ecd540

 ("iommu/vt-d: Clean up unused PASID updating functions")
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20211123105507.7654-2-joro@8bytes.org