fix(kscan): Remove warning when keyboard is built without CONFIG_PM_DEVICE (#2808)

Author: nmunnich

app/module/drivers/kscan/kscan_gpio_charlieplex.c

@@ -168,6 +168,8 @@ static int kscan_charlieplex_set_all_outputs(const struct device *dev, const int
     return 0;
 }
 
+#if IS_ENABLED(CONFIG_PM_DEVICE)
+
 static int kscan_charlieplex_disconnect_all(const struct device *dev) {
     const struct kscan_charlieplex_config *config = dev->config;
 
@@ -183,6 +185,8 @@ static int kscan_charlieplex_disconnect_all(const struct device *dev) {
     return 0;
 }
 
+#endif
+
 static int kscan_charlieplex_interrupt_configure(const struct device *dev,
                                                  const gpio_flags_t flags) {
     const struct kscan_charlieplex_config *config = dev->config;