powerpc: Reduce scariness of interrupt frames in stack traces

Some people see things like "Exception: 501" in stack traces in dmesg
and assume that means that something has gone badly wrong, when in
fact "Exception: 501" just means a device interrupt was taken.
This changes "Exception" to "interrupt" to make it clearer that we
are just recording the fact of a change in control flow rather than
some error condition.
Signed-off-by: NPaul Mackerras <paulus@samba.org>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/process.c

@@ -1581,7 +1581,7 @@ void show_stack(struct task_struct *tsk, unsigned long *stack)
 			struct pt_regs *regs = (struct pt_regs *)
 				(sp + STACK_FRAME_OVERHEAD);
 			lr = regs->link;
-			printk("--- Exception: %lx at %pS\n    LR = %pS\n",
+			printk("--- interrupt: %lx at %pS\n    LR = %pS\n",
 			       regs->trap, (void *)regs->nip, (void *)lr);
 			firstframe = 1;
 		}