common: arm: Move s_init() to an ARM-specific header

This function is only used on ARM devices so does not belong in the global
common header file. Move it to an ARM header.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/include/asm/u-boot-arm.h b/arch/arm/include/asm/u-boot-arm.h
index 2e8c8e5..62cb5b4 100644
--- a/arch/arm/include/asm/u-boot-arm.h
+++ b/arch/arm/include/asm/u-boot-arm.h
@@ -23,6 +23,8 @@
 extern ulong _datarelro_start_ofs;
 extern ulong IRQ_STACK_START_IN;	/* 8 bytes in IRQ stack */
 
+void s_init(void);
+
 /* cpu/.../cpu.c */
 int	cleanup_before_linux(void);
 
diff --git a/include/common.h b/include/common.h
index 463eeb5..f38dc2e 100644
--- a/include/common.h
+++ b/include/common.h
@@ -74,8 +74,6 @@
 int testdram(void);
 #endif /* CONFIG_SYS_DRAM_TEST */
 
-void s_init(void);
-
 void	upmconfig     (unsigned int, unsigned int *, unsigned int);
 ulong	get_tbclk     (void);
 void	reset_misc    (void);