ARM: dts: msm: Use mock retention sequence for A57 CPUs on MSM8992

Use mock retention sequence for the A57 cpus. This is to workaround
issues due to missing level shifters in the hardware. This would allow
power savings from L1 memory in retention, while avoiding cache
corruption issues due to L1 logic going in and out of retention.

Change-Id: If19147d6b15c2ca9b06bd44fe0eb03dcd908d743
Signed-off-by: Karthik Parsha <kparsha@codeaurora.org>