[ARM] 4488/1: pxa: move pxa25x/pxa27x specific code out of pm.c

1. introduce a structure pxa_cpu_pm_fns for pxa25x/pxa27x specific
   operations as follows:

	struct pxa_cpu_pm_fns {
		int	save_size;
		void	(*save)(unsigned long *);
		void	(*restore)(unsigned long *);
		int	(*valid)(suspend_state_t state);
		void	(*enter)(suspend_state_t state);
	}

2. processor specific registers saving and restoring are performed
   by calling the corresponding (*save) and (*restore)

3. pxa_cpu_pm_fns->save_size should be initialized to the required
   size for processor specific registers saving, the allocated
   memory address will be passed to (*save) and (*restore)

   memory allocation happens early in pxa_pm_init(), and save_size
   should be assigned prior to this (which is usually true, since
   pxa_pm_init() happens in device_initcall()

4. there're some redundancies for those SLEEP_SAVE_XXX and related
   macros, will be fixed later, one way possible is for the system
   devices to handle the specific registers saving and restoring

Signed-off-by: eric miao <eric.y.miao@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>