msm: subsystem_restart: Use a CPU intensive workqueue for SSR

Using the default workqueue settings can result in the SSR
work item blocking the watchdog petting function. To avoid
this, schedule the SSR work on a workqueue that has the
WQ_CPU_INTENSIVE flag set. This will prevent any work item
posted to the workqueue from blocking other work items
posted by other drivers in the system, including the watchdog
pet work item.

Change-Id: I159f8c5aba9ff3b40f61bdb101f266436bd2c9bc
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>