iommu: msm: Add support for selecting remote spinlock in device tree

Certain SoCs need to aquire a remote spinlock before accessing SMMU
registers. This adds support for specifying in the device tree which
SMMUs must take the remote spinlock.

CRs-fixed: 517873
Change-Id: I28582c137d2ff4f98c982b5a12aa6fd3c9e295bc
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>