riscv: Make stack walk callback consistent with generic code

In order to use generic arch_stack_walk() code, make stack walk
callback consistent with it.

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

arch/riscv/include/asm/stacktrace.h

@@ -12,6 +12,6 @@ struct stackframe {
 };
 
 extern void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
-				    bool (*fn)(unsigned long, void *), void *arg);
+				    bool (*fn)(void *, unsigned long), void *arg);
 
 #endif /* _ASM_RISCV_STACKTRACE_H */