soc: qcom: cpu_ops: remove unused code for msm8996 and msm8994

msm8996 now only supports bringing CPUs online and offline via PSCI.
Drop the now-unused code that was needed for the "qcom,msm8996-acc"
enable method.

While we're at it, also delete the unused cpu and power control
functions for msm8994. General support for this target does not
exist in this kernel branch, so there's no point building the
code or keeping it around.

Change-Id: I3a74d529b080de92ae4c1e095c3e60ce0ea51103
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>