cpuidle: qcom_spm: Detach state machine from main SPM handling

cpuidle: qcom_spm: Detach state machine from main SPM handling

In commit a871be6b8eee ("cpuidle: Convert Qualcomm SPM driver to a generic
CPUidle driver") the SPM driver has been converted to a
generic CPUidle driver: that was mainly made to simplify the
driver and that was a great accomplishment;
Though, at that time, this driver was only applicable to ARM 32-bit SoCs,
lacking logic about the handling of newer generation SAW.

In preparation for the enablement of SPM features on AArch64/ARM64,
split the cpuidle-qcom-spm driver in two: the CPUIdle related
state machine (currently used only on ARM SoCs) stays there, while
the SPM communication handling lands back in soc/qcom/spm.c and
also making sure to not discard the simplifications that were
introduced in the aforementioned commit.

Since now the "two drivers" are split, the SCM dependency in the
main SPM handling is gone and for this reason it was also possible
to move the SPM initialization early: this will also make sure that
whenever the SAW CPUIdle driver is getting initialized, the SPM
driver will be ready to do the job.

Please note that the anticipation of the SPM initialization was
also done to optimize the boot times on platforms that have their
CPU/L2 idle states managed by other means (such as PSCI), while
needing SAW initialization for other purposes, like AVS control.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org>
Reviewed-by: Stephan Gerhold <stephan@gerhold.net>
Tested-by: Stephan Gerhold <stephan@gerhold.net>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20210729155609.608159-2-angelogioacchino.delregno@somainline.org