msm: restart: Handle reset interrupt from pmic

The reset interrupt in the pmic indicates the pmic will shutdown
the msm in few seconds - it does so by lowering the reset_n line
to the msm.

When this interrupt is triggered it is required that no more ssbi
transactions are initiated and the msm should cleanup and prepare
for the impending shutdown. There is no need to lower ps_hold in
this case as the pmic will shutdown the msm regardless.

Also since we don't want any ssbi transactions, force shutdown
nonboot cpus. This will prevent ssbi transactions to the pmic for
lower/raising nonboot cpu's voltages as they enter/exit idle states.

Change-Id: If2b392c2a0494356f17bf3b721e396da2af44dd2
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>
[sboyd: take header part only]
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>