intel-iommu: remove slpte present check

There is no 'present' concept in slpte entry. There are only read/write
permissions. So remove slpte_present() and just check the access right.

Signed-off-by: Le Tan <tamlokveer@gmail.com>
intel-iommu: clean up some unused macro definitions

Clean up some unused macro definitions.

Signed-off-by: Le Tan <tamlokveer@gmail.com>