iommu/arm-smmu: Fix SMMU derivation in arm_smmu_power_off_atomic

The arm_smmu_power_off_atomic() function derives the pointer to
the SMMU device by incorrectly assuming that all devices in the
power resources structures store that pointer as part of their
driver data.

While this is true for devices that represent an SMMU, this is
not the case for the devices that represent the TBUs, as they
store the TBU structures instead of a pointer to the SMMU device.
Thus, require the SMMU device as a parameter to the
arm_smmu_power_off[_atomic] functions so that it can be used
correctly.

Change-Id: I0101500468afe17456bd6178082850e5fa6590d7
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>