ANDROID: iommu: Kconfig: Make ARM_SMMU depend on QCOM_SCM || !QCOM_SCM

The arm-smmu-qcom code calls qcom_scm_qsmmu500_wait_safe_toggle().
Since the QCOM_SCM config can now be set as a module, this
requires the ARM_SMMU also be a module in that case, so make
the dependency explicit in the Kconfig.

This is done via the non-intuitive "depends on QCOM_SCM || !QCOM_SCM"
Kconfig syntax, which basically ensures that QCOM_SCM isn't
configured as a module if ARM_SMMU is built in.

Fixes: 6a1652ef ("ANDROID: firmware: QCOM_SCM: Allow qcom_scm driver to be loadable as a permenent module")
Signed-off-by: John Stultz <john.stultz@linaro.org>
Change-Id: I580e65e3df85bfbda2af5c54a1a068f6de7d27ee