[IA64] Extract correct break number for break.b

break.b does not store the break number in cr.iim, instead it stores 0,
which makes all break.b instructions look like BUG().  Extract the
break number from the instruction itself.

Signed-off-by: Keith Owens <kaos@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>