msm: pm: Remove log messages for hotplug

The log messages to indicate a system entering low power mode during
suspend are also being printed for a cpu hotplug and floods the system
log buffer. Print the log message for suspend operation only and ignore
them during the hotplug path.

Change-Id: I0cdeab5f0e58bb7524c51e3801802a1cfc37c6c3
Signed-off-by: Mahesh Sivasubramanian <msivasub@codeaurora.org>