sparc64: Fix build errors with gcc-4.6.0

Most of the warnings emitted (we fail arch/sparc file
builds with -Werror) were legitimate but harmless, however
one case (n2_pcr_write) was a genuine bug.

Based almost entirely upon a patch by Sam Ravnborg.

Reported-by: Dennis Gilmore <dennis@ausil.us>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/arch/sparc/kernel/traps_64.c b/arch/sparc/kernel/traps_64.c
index 1e97709..1ed547b 100644
--- a/arch/sparc/kernel/traps_64.c
+++ b/arch/sparc/kernel/traps_64.c
@@ -2152,7 +2152,7 @@
 
 void show_stack(struct task_struct *tsk, unsigned long *_ksp)
 {
-	unsigned long fp, thread_base, ksp;
+	unsigned long fp, ksp;
 	struct thread_info *tp;
 	int count = 0;
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
@@ -2173,7 +2173,6 @@
 		flushw_all();
 
 	fp = ksp + STACK_BIAS;
-	thread_base = (unsigned long) tp;
 
 	printk("Call Trace:\n");
 	do {