ARM: dts: imx51-zii-rdu1: Add the unit addresses in sysled

As described at Documentation/devicetree/bindings/mfd/mc13xxx.txt the
reg property is mandatory, so add the corresponding unit address in
order to fix the following build warnings with W=1:

arch/arm/boot/dts/imx51-zii-rdu1.dtb: Warning (unit_address_vs_reg): Node /soc/aips@70000000/spba@70000000/ecspi@70010000/pmic@0/leds/sysled0 has a reg or ranges property, but no unit name
arch/arm/boot/dts/imx51-zii-rdu1.dtb: Warning (unit_address_vs_reg): Node /soc/aips@70000000/spba@70000000/ecspi@70010000/pmic@0/leds/sysled1 has a reg or ranges property, but no unit name

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>