ARM: shmobile: ape6evm: add CPUFreq support

This patch adds OPPs to the CA15 DT node and a max8973 DT node to support
clock and voltage scaling, using the cpufreq-cpu0 CPUFreq driver.

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