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

To circumvent issues around A57 retention, use mock retention sequence that
clamps L1 only during retention and doesn't place the CPU logic under
retention.

Change-Id: I9b7e978ec98e75876f93f485da6ee0705cc4a3cf
Signed-off-by: Mahesh Sivasubramanian <msivasub@codeaurora.org>