iommu/arm-smmu: Remove 'qcom,power-always-on' property for SMMU

The commit 8ffa6450 ("iommu/arm-smmu: Add support for not removing
SMMU power votes") add the support for not removing the power votes of
smmu. It requires 'qcom,power-always-on' in smmu dt property to enable
this support which is currently enabled only for gpu smmu. And this
makes the clients of the SMMU to know If this dt property is enabled to
make decissions in their drivers which is not directly available.

Since there exists a device with atomic domain attached to apps smmu
which will make power resources always on, this separate dt property to
enable power resources for specific SMMU is not required. Thus remove
the 'qcom,power-always-on' property which makes power resources of
SMMU's as always ON when CONFIG_ARM_SMMU_POWER_ALWAYS_ON is enabled.

Change-Id: I2ee1d330f5c1c65474fea7d6b2a9389ae3cf085d
Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>