ARM: provide an early platform initialization hook

This allows platforms to hook into the initialization early to setup
things like scheduler clocks, etc.

Signed-off-by: Russell King <[e-mail]>

arch/arm/include/asm/mach/arch.h

···
 					 struct meminfo *);
 	void			(*reserve)(void);/* reserve mem blocks	*/
 	void			(*map_io)(void);/* IO mapping function	*/
+	void			(*init_early)(void);
 	void			(*init_irq)(void);
 	struct sys_timer	*timer;		/* system tick timer	*/
 	void			(*init_machine)(void);

arch/arm/kernel/setup.c

···
 #endif
 #endif
 	early_trap_init();
+
+	if (mdesc->init_early)
+		mdesc->init_early();
 }