ARM: dts: imx53-ppd: alarm LEDs use kernel LED interface

Use kernel LED interface for the alarm LEDs.

Signed-off-by: Ian Ray <ian.ray@ge.com>
Signed-off-by: Samu Nuutamo <samu.nuutamo@vincit.fi>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>