i3c: master: make i3c_bus_set_mode static

i3c_bus_set_mode function is only used in master.c.
Make it static to avoid warning when compiling with W=1.
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>

drivers/i3c/master.c

@@ -527,8 +527,8 @@ static const struct device_type i3c_masterdev_type = {
 	.groups	= i3c_masterdev_groups,
 };
 
-int i3c_bus_set_mode(struct i3c_bus *i3cbus, enum i3c_bus_mode mode,
-		     unsigned long max_i2c_scl_rate)
+static int i3c_bus_set_mode(struct i3c_bus *i3cbus, enum i3c_bus_mode mode,
+			    unsigned long max_i2c_scl_rate)
 {
 	struct i3c_master_controller *master = i3c_bus_to_i3c_master(i3cbus);