ARM: s3c: remove unused declarations for s3c6400

These declarations for s3c6400 have been removed since
commit 6bac4f7 ("ARM: s3c: remove s3c6400 support"), so
remove it.

Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Link: https://lore.kernel.org/r/20240813105545.1180788-2-cuigaosheng1@huawei.com
Fixes: 6bac4f7 ("ARM: s3c: remove s3c6400 support")
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Author: gscui

arch/arm/mach-s3c/s3c64xx.h

@@ -23,17 +23,6 @@ struct device_node;
 void s3c64xx_set_xtal_freq(unsigned long freq);
 void s3c64xx_set_xusbxti_freq(unsigned long freq);
 
-#ifdef CONFIG_CPU_S3C6400
-
-extern  int s3c6400_init(void);
-extern void s3c6400_init_irq(void);
-extern void s3c6400_map_io(void);
-
-#else
-#define s3c6400_map_io NULL
-#define s3c6400_init NULL
-#endif
-
 #ifdef CONFIG_CPU_S3C6410
 
 extern  int s3c6410_init(void);