soc: qcom: Add snapshot for smp2p sleepstate driver

This snapshot is taken as of msm-4.14 'commit <5043ac1ca6a6>
("Merge "drivers: mailbox: rpmh: Use high priority tasklet"")'.

In addition change copyrights to SPDX format and fix init error
handling and prints.

Change-Id: I56febbc674ccaafbb20fc0837ffd193c99ab47f2
Signed-off-by: Chris Lew <clew@codeaurora.org>