ARM: dts: Use label for device nodes in Cygnus dts

Use label instead of full path to reference device nodes in Cygnus dts
files

Signed-off-by: Ray Jui <rjui@broadcom.com>
Reviewed-by: Scott Branden <sbranden@broadcom.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>