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

arch/sparc/kernel/entry.S

@@ -293,7 +293,7 @@ maybe_smp4m_msg:
 	WRITE_PAUSE
 	wr	%l4, PSR_ET, %psr
 	WRITE_PAUSE
-	sll	%o3, 28, %o2		! shift for simpler checks below
+	srl	%o3, 28, %o2		! shift for simpler checks below
 maybe_smp4m_msg_check_single:
 	andcc	%o2, 0x1, %g0
 	beq,a	maybe_smp4m_msg_check_mask