powerpc/ftrace: Refactor ftrace_{en/dis}able_ftrace_graph_caller

ftrace_enable_ftrace_graph_caller() and
ftrace_disable_ftrace_graph_caller() have common code.

They will have even more common code after following patch.

Refactor into a single ftrace_modify_ftrace_graph_caller() function.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/f37785a531f1a8f201e1b3da45997a5c77e9d820.1640017960.git.christophe.leroy@csgroup.eu

arch/powerpc/kernel/trace/ftrace.c

@@ -910,30 +910,27 @@ int __init ftrace_dyn_arch_init(void)
 extern void ftrace_graph_call(void);
 extern void ftrace_graph_stub(void);
 
-int ftrace_enable_ftrace_graph_caller(void)
+static int ftrace_modify_ftrace_graph_caller(bool enable)
 {
 	unsigned long ip = (unsigned long)(&ftrace_graph_call);
 	unsigned long addr = (unsigned long)(&ftrace_graph_caller);
 	unsigned long stub = (unsigned long)(&ftrace_graph_stub);
 	ppc_inst_t old, new;
 
-	old = ftrace_call_replace(ip, stub, 0);
-	new = ftrace_call_replace(ip, addr, 0);
+	old = ftrace_call_replace(ip, enable ? stub : addr, 0);
+	new = ftrace_call_replace(ip, enable ? addr : stub, 0);
 
 	return ftrace_modify_code(ip, old, new);
 }
 
-int ftrace_disable_ftrace_graph_caller(void)
+int ftrace_enable_ftrace_graph_caller(void)
 {
-	unsigned long ip = (unsigned long)(&ftrace_graph_call);
-	unsigned long addr = (unsigned long)(&ftrace_graph_caller);
-	unsigned long stub = (unsigned long)(&ftrace_graph_stub);
-	ppc_inst_t old, new;
-
-	old = ftrace_call_replace(ip, addr, 0);
-	new = ftrace_call_replace(ip, stub, 0);
+	return ftrace_modify_ftrace_graph_caller(true);
+}
 
-	return ftrace_modify_code(ip, old, new);
+int ftrace_disable_ftrace_graph_caller(void)
+{
+	return ftrace_modify_ftrace_graph_caller(false);
 }
 
 /*