ARM: dts: socfpga: align LED node names with dtschema

The node names should be generic and DT schema expects certain pattern:

  socfpga_arria5_socdk.dtb: leds: 'hps0', 'hps1', 'hps2', 'hps3' do not match any of the regexes: '(^led-[0-9a-f]$|led)', 'pinctrl-[0-9]+'

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>