ARM: shmobile: parse DT and configure pinmux early on kzm9g-reference

GPIOs can be provided by the pinctrl subsystem, which can be initialised
by DT. Therefore DT has to be parsed before requesting GPIOs. Also non-DT
pinmux has to be configured early.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>