ARM: dts: imx28-sps1: Fix GPIO LEDs description

ARM: dts: imx28-sps1: Fix GPIO LEDs description

According to leds-gpio.yaml, the LED nodes should not contain
unit addresses. Remove them.

Also, 'default-trigger' is not a valid property. Change it to
'linux,default-trigger'.

These changes fix the following dt-schema warnings:

led@1: Unevaluated properties are not allowed ('reg' was unexpected)
led@2: Unevaluated properties are not allowed ('reg' was unexpected)
led@3: Unevaluated properties are not allowed ('default-trigger', 'reg' were unexpected)
leds: '#address-cells', '#size-cells' do not match any of the regexes: '(^led-[0-9a-f]$|led)', 'pinctrl-[0-9]+'

Signed-off-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>