iommu/arm-smmu: fix panic in arm_smmu_alloc_init_pte

kernel panic happened when iommu_unmap a buffer larger than 2MB,
more than expected pmd entries got “invalidated”, due to a wrong range
passed to arm_smmu_alloc_init_pte. it was likely a typo, now we fix
it, passing the correct "end" address to arm_smmu_alloc_init_pte.

Signed-off-by: Bin Wang <binw@marvell.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>