ARM: at91: pm: Move prototypes to mutually included header

Both the caller and the supplier's source file should have access to
the include file containing the prototypes.

Fixes the following W=1 kernel build warning(s):

drivers/pinctrl/pinctrl-at91.c:1637:6: warning: no previous prototype for ‘at91_pinctrl_gpio_suspend’ [-Wmissing-prototypes]
1637 | void at91_pinctrl_gpio_suspend(void)
| ^~~~~~~~~~~~~~~~~~~~~~~~~
drivers/pinctrl/pinctrl-at91.c:1661:6: warning: no previous prototype for ‘at91_pinctrl_gpio_resume’ [-Wmissing-prototypes]
1661 | void at91_pinctrl_gpio_resume(void)
| ^~~~~~~~~~~~~~~~~~~~~~~~

Cc: Russell King <[e-mail]>
Cc: Nicolas Ferre <[e-mail]>
Cc: Alexandre Belloni <[e-mail]>
Cc: Ludovic Desroches <[e-mail]>
Signed-off-by: Lee Jones <[e-mail]>
Acked-by: Linus Walleij <[e-mail]>
Signed-off-by: Alexandre Belloni <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

arch/arm/mach-at91/pm.c

···
 #include <linux/clk/at91_pmc.h>
 #include <linux/platform_data/atmel.h>
 
+#include <soc/at91/pm.h>
+
 #include <asm/cacheflush.h>
 #include <asm/fncpy.h>
 #include <asm/system_misc.h>
···
 
 #include "generic.h"
 #include "pm.h"
-
-/*
- * FIXME: this is needed to communicate between the pinctrl driver and
- * the PM implementation in the machine. Possibly part of the PM
- * implementation should be moved down into the pinctrl driver and get
- * called as part of the generic suspend/resume path.
- */
-#ifdef CONFIG_PINCTRL_AT91
-extern void at91_pinctrl_gpio_suspend(void);
-extern void at91_pinctrl_gpio_resume(void);
-#endif
 
 struct at91_soc_pm {
 	int (*config_shdwc_ws)(void __iomem *shdwc, u32 *mode, u32 *polarity);
···
 static int at91_pm_enter(suspend_state_t state)
 {
 #ifdef CONFIG_PINCTRL_AT91
+	/*
+	 * FIXME: this is needed to communicate between the pinctrl driver and
+	 * the PM implementation in the machine. Possibly part of the PM
+	 * implementation should be moved down into the pinctrl driver and get
+	 * called as part of the generic suspend/resume path.
+	 */
 	at91_pinctrl_gpio_suspend();
 #endif
 

drivers/pinctrl/pinctrl-at91.c

···
 /* Since we request GPIOs from ourself */
 #include <linux/pinctrl/consumer.h>
 
+#include <soc/at91/pm.h>
+
 #include "pinctrl-at91.h"
 #include "core.h"
 

include/soc/at91/pm.h

···
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Atmel Power Management
+ *
+ * Copyright (C) 2020 Atmel
+ *
+ * Author: Lee Jones <[e-mail]>
+ */
+
+#ifndef __SOC_ATMEL_PM_H
+#define __SOC_ATMEL_PM_H
+
+void at91_pinctrl_gpio_suspend(void);
+void at91_pinctrl_gpio_resume(void);
+
+#endif /* __SOC_ATMEL_PM_H */