[IA64-SGI] Change SAL call request code for SN systems

Change the value of the SAL call number for a new SAL request. The
initial implementation in the PROM did not match what the OS expected. 
Since the OS can run on PROMs that do not implement the new call, 
changing the call number avoids the issue. New PROMs will implement
the new call number. (This avoids problems with the 4.05 PROM).

Signed-off-by: Jack Steiner <steiner@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>