riscv: Cleanup stacktrace

1. add asm/stacktrace.h for walk_stackframe and struct stackframe
2. remove unnecessary blank lines in stacktrace.c
3. fix warning "no previous prototype for ‘fill_callchain’"

Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

arch/riscv/kernel/stacktrace.c

@@ -12,15 +12,12 @@
 #include <linux/stacktrace.h>
 #include <linux/ftrace.h>
 
+#include <asm/stacktrace.h>
+
 register unsigned long sp_in_global __asm__("sp");
 
 #ifdef CONFIG_FRAME_POINTER
 
-struct stackframe {
-	unsigned long fp;
-	unsigned long ra;
-};
-
 void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
 			     bool (*fn)(unsigned long, void *), void *arg)
 {
@@ -96,7 +93,6 @@ void notrace walk_stackframe(struct task_struct *task,
 
 #endif /* CONFIG_FRAME_POINTER */
 
-
 static bool print_trace_address(unsigned long pc, void *arg)
 {
 	const char *loglvl = arg;
@@ -130,7 +126,6 @@ unsigned long get_wchan(struct task_struct *task)
 	return pc;
 }
 
-
 #ifdef CONFIG_STACKTRACE
 
 static bool __save_trace(unsigned long pc, void *arg, bool nosched)