ARM: dts: omap4-droid4: Update backlight dt properties

Update the properties for the lm3532 device node for droid4.
With this change the backlight LED string and the keypad
LED strings will be controlled separately.

Signed-off-by: Dan Murphy <dmurphy@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
[tony@atomide.com: remove the line "backlight = <&lcd_backlight>"]
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>