arm64: Dump stack for all CPUs on SMP CPU stop

Add the stack dump and printk of other CPUs when they are stopped
during an abnormal operation like a panic - This information is useful
for debugging to get a clear idea of what might have caused a crash.

Change-Id: I91a62cfc7cdb49b9cdbb247869b5ba799947ece5
Signed-off-by: Kyle Yan <kyan@codeaurora.org>