firmware: arm_scpi: Revert updates made during v4.15 merge window

Revert "Merge tag 'scpi-updates-4.15' of git://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux

 into next/drivers"

Paraphrased from email from Kevin Hilman:

Revert ARM SCPI changes since v4.14.

Untested changes caused regressions in SCPI and CPUfreq/DVFS failures
on most Amlogic SoCs.  Changes reverted for v4.15 so they can be better
reviewed and tested.

These ARM SCPI changes caused SCPI regressions resulting in CPUfreq
failures on most Amlogic SoCs (found by kernelci.org.)

Unfortunately, this was not caught in linux-next due to other bugs/panics
on these platforms masking this problem so we've only found it since
we've fixed the other issues.

Since we're already in the -rc cycle, I'd prefer to revert to a known
working state (that of v4.14) rather than finding/reverting a subset,
which would just lead to another untested state.

These changes can then have some time to be better reviewed and tested
and resubmitted for v4.16.

Kevin Hilman has tested this revert on the affected Amlogic SoCs and
verified that we're back to the previous (working) condition.

This reverts commit 6710acf2, reversing
changes made to 4b367f2e.

Reported-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Olof Johansson <olof@lixom.net>