iommu: msm: Program non secure registers only in non secure environment

The non secure registers in IOMMU are programmed when
CONFIG_IOMMU_NON_SECURE is enabled. The programming of these registers
is no longer dependent on this config, but depends on a check to see
if the secure environment is available.

CONFIG_IOMMU_NON_SECURE is now only used to force all SMMUs to be
programmed by the Linux kernel SMMU driver for debugging purposes.

Change-Id: I367f92fd6e5198395b83e6ca8acde66b1b012620
Signed-off-by: Neeti Desai <neetid@codeaurora.org>