[IA64] Delete MCA/INIT sigdelayed code

The only user of the MCA/INIT sigdelayed code (SGI's I/O probing) has
moved from the kernel into SAL.  Delete the MCA/INIT sigdelayed code.

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