LoongArch: Fix definition of ftrace_regs_set_instruction_pointer()

The current definition of ftrace_regs_set_instruction_pointer() is not
correct. Obviously, this function is used to set instruction pointer but
not return value, so it should call instruction_pointer_set() instead of
regs_set_return_value().

There is no side effect by now because it is only used for kernel live-
patching which is not supported, so fix it to avoid failure when testing
livepatch in the future.

Fixes: 6fbff14a ("LoongArch: ftrace: Abstract DYNAMIC_FTRACE_WITH_ARGS accesses")
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/include/asm/ftrace.h

@@ -63,7 +63,7 @@ ftrace_regs_get_instruction_pointer(struct ftrace_regs *fregs)
 static __always_inline void
 ftrace_regs_set_instruction_pointer(struct ftrace_regs *fregs, unsigned long ip)
 {
-	regs_set_return_value(&fregs->regs, ip);
+	instruction_pointer_set(&fregs->regs, ip);
 }
 
 #define ftrace_regs_get_argument(fregs, n) \