ARM: shmobile: ape6evm: Add GPIO LEDs

The board has 6 LEDs connected to GPIOs. Add a led-gpio device to
support them.

Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>