sh: Only invalidate the I-cache range for secondary CPUs stack_start.

Secondary CPUs already take care of the D-cache bits through the common
cache initialization path, and the only thing that is necessary after
twiddling around with stack_start is ensuring that the I-cache changes
are visible (particularly since this tends to be the only part lacking
coherency).
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>

arch/sh/kernel/smp.c

@@ -120,7 +120,9 @@ int __cpuinit __cpu_up(unsigned int cpu)
 	stack_start.bss_start = 0; /* don't clear bss for secondary cpus */
 	stack_start.start_kernel_fn = start_secondary;
 
-	flush_cache_all();
+	flush_icache_range((unsigned long)&stack_start,
+			   (unsigned long)&stack_start + sizeof(stack_start));
+	wmb();
 
 	plat_start_cpu(cpu, (unsigned long)_stext);