[IA64] dump stack on kernel unaligned warnings

Often the cause of kernel unaligned access warnings is not
obvious from just the ip displayed in the warning.  This adds
the option via proc to dump the stack in addition to the warning.
The default is off (just display the 1 line warning).  To enable
the stack to be shown: echo 1 > /proc/sys/kernel/unaligned-dump-stack

Signed-off-by: Doug Chapman <doug.chapman@hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>