leds: new class for led devices

This is an attempt to provide an alternative to the current arm specific led interface. This arm interface does not integrate well with the device model and sysfs.

We create a new class that drivers can register a leds_properties structure with. Each led that is registered is assigned a number, and three attributes are exported to sysfs in /sys/class/leds/1/, /sys/class/leds/2, etc.

color : a read only string attribute that shows the available colors of this led. If it is a multi-color led, then the colors are seperated by a "/" (for example "green/blue").

function : a read/write attribute that sets the current function of this led. The available options are

timer : the led blinks on and off on a timer
idle : the led turns off when the system is idle and on when not idle power : the led represents the current power state
user : the led is controlled by user space

light : a read/write attribute that allows userspace to see the current status of the led. If function="user" then writing to this attribute will change the led on or off. If function != "user" then writing has no effect.
light is an integer, where 0 means off, 1 means on first color, 2
means on second color, etc. (for example, if color="green/blue" then light=1 means turn led on to green and if light=2 means turn led on to blue.

A device and driver symlink point to the actual driver and such, so any extra attributes can also be registered.