iommu/arm-smmu: sign extend iova for fault handler

The address in the CB's FAR is not sign-extended. With split page tables,
this can cause software page table walk causing warning.

WARNING: CPU: 2 PID: 264 at drivers/iommu/arm-smmu.c:3161 arm_smmu_iova_to_phys+0xfc/0x128
kgsl kgsl-3d0: CP Illegal instruction error
kgsl kgsl-3d0: CP Illegal instruction error
kgsl kgsl-3d0: CP Illegal instruction error
kgsl kgsl-3d0: CP Illegal instruction error
pc : arm_smmu_iova_to_phys+0xfc/0x128
lr : arm_smmu_context_fault+0x188/0xea4

Perform the sign extension in fault handler, as arm_smmu_iova_to_phys()
expects the IOVA to be sign extended.

Fixes: ff4f3466 ("iommu/arm-smmu: Add support for split page table domains")
Change-Id: Iced0b7a518dbc27b2770fdae47bedce4e72cc3c1
Signed-off-by: Prakash Gupta <guptap@codeaurora.org>