clk: samsung: s3c64xx: declare s3c64xx_clk_init() in shared header

The s3c64xx_clk_init() is defined and used by the clk-s3c64xx driver and
also used in the mach-s3c64xx machine code.  Move the declaration to a
header to fix W=1 build warning:

    drivers/clk/samsung/clk-s3c64xx.c:391:13: warning: no previous prototype for 's3c64xx_clk_init' [-Wmissing-prototypes]
      391 | void __init s3c64xx_clk_init(struct device_node *np, unsigned long xtal_f,
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Tomasz Figa <tomasz.figa@gmail.com>
Acked-by: Chanwoo Choi <cw00.choi@samsung.com>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>

MAINTAINERS

@@ -15304,6 +15304,7 @@ F:	Documentation/devicetree/bindings/clock/samsung,s3c*
 F:	Documentation/devicetree/bindings/clock/samsung,s5p*
 F:	drivers/clk/samsung/
 F:	include/dt-bindings/clock/exynos*.h
+F:	include/linux/clk/samsung.h
 
 SAMSUNG SPI DRIVERS
 M:	Kukjin Kim <kgene@kernel.org>

arch/arm/mach-s3c64xx/common.c

@@ -24,6 +24,7 @@
 #include <linux/platform_device.h>
 #include <linux/reboot.h>
 #include <linux/io.h>
+#include <linux/clk/samsung.h>
 #include <linux/dma-mapping.h>
 #include <linux/irq.h>
 #include <linux/gpio.h>

arch/arm/mach-s3c64xx/common.h

@@ -22,8 +22,6 @@ void s3c64xx_init_io(struct map_desc *mach_desc, int size);
 void s3c64xx_restart(enum reboot_mode mode, const char *cmd);
 
 struct device_node;
-void s3c64xx_clk_init(struct device_node *np, unsigned long xtal_f,
-	unsigned long xusbxti_f, bool is_s3c6400, void __iomem *reg_base);
 void s3c64xx_set_xtal_freq(unsigned long freq);
 void s3c64xx_set_xusbxti_freq(unsigned long freq);
 

drivers/clk/samsung/clk-s3c64xx.c

@@ -7,6 +7,7 @@
 
 #include <linux/slab.h>
 #include <linux/clk-provider.h>
+#include <linux/clk/samsung.h>
 #include <linux/of.h>
 #include <linux/of_address.h>
 

include/linux/clk/samsung.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2020 Krzysztof Kozlowski <krzk@kernel.org>
+ */
+
+#ifndef __LINUX_CLK_SAMSUNG_H_
+#define __LINUX_CLK_SAMSUNG_H_
+
+#include <linux/compiler_types.h>
+
+struct device_node;
+
+#ifdef CONFIG_ARCH_S3C64XX
+void s3c64xx_clk_init(struct device_node *np, unsigned long xtal_f,
+		      unsigned long xusbxti_f, bool s3c6400,
+		      void __iomem *base);
+#else
+static inline void s3c64xx_clk_init(struct device_node *np,
+				    unsigned long xtal_f,
+				    unsigned long xusbxti_f,
+				    bool s3c6400, void __iomem *base) { }
+#endif /* CONFIG_ARCH_S3C64XX */
+
+#endif /* __LINUX_CLK_SAMSUNG_H_ */