Current SHPCHP driver doesn't care about the confliction between
hotplug operation via sysfs and hotplug operation via attention
button. So if those ware conflicted, slot could be an unexpected
state.

This patch changes SHPCHP driver to handle slot state properly. With
this patch, slot events are handled according to the current slot
state as shown at the Table below.

		Table. Slot States and Event Handling
=========================================================================
Slot State		Event and Action
=========================================================================
STATIC			- Go to POWERON state if user initiates
(Slot enabled,		  insertion request via sysfs
 Slot disabled)		- Go to POWEROFF state if user initiates removal
			  request via sysfs
			- Go to BLINKINGON state if user presses
			  attention button when the slot is disabled
			- Go to BLINKINGOFF state if user presses
			  attention button when the slot is enabled