sparc: sun4m SMP: fix wrong shift instruction in IPI handler

This shift instruction appears to be shifting in the wrong direction.
Without this change, my SparcStation-20MP hangs just after bringing up
the second CPU:

Entering SMP Mode...
Starting CPU 2 at f02b4e90
Brought up 2 CPUs
Total of 2 processors activated (99.52 BogoMIPS).
   *** stuck ***

Signed-off-by: Will Simoneau <simoneau@ele.uri.edu>
Signed-off-by: David S. Miller <davem@davemloft.net>