iommu/io-pgtable-arm: Remove unused macro iopte_prot

iommu/io-pgtable-arm: Remove unused macro iopte_prot

Commit 33729a5fc0ca ("iommu/io-pgtable-arm: Remove split on unmap
behavior") removed the last user of the macro iopte_prot. Remove the
macro definition of iopte_prot as well as three other related
definitions.

Fixes: 33729a5fc0ca ("iommu/io-pgtable-arm: Remove split on unmap behavior")
Signed-off-by: Daniel Mentz <danielmentz@google.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20250708211705.1567787-1-danielmentz@google.com
Signed-off-by: Will Deacon <will@kernel.org>