msm: spm: Add support to trigger SPM with q-channel for clock gating

On some targets, the SPM can be triggered using a Q-channel instead of
relying on wfi to trigger a low power mode. As wfe command also triggers
the Q-channel, SPM can be triggered for clock gating using wfe as well.
This along side the SPM commands to stagger a wakeup of a core, can be used
to stagger wake up out of wfi/wfe using SPM.

Change-Id: Ie2897607c7361f2b6c291f68f27d3929a4fd0cb3
Signed-off-by: Mahesh Sivasubramanian <msivasub@codeaurora.org>