arm: vf610: Add IOMUX support for Vybrid VF610

This patch adds the IOMUX support for Vybrid VF610 platform.

There is a little difference for IOMUXC module between VF610 and i.MX
platform, the muxmode and pad configuration share one 32bit register on
VF610, but they are two independent registers on I.MX platform. A
CONFIG_IOMUX_SHARE_CONFIG_REG was introduced to fit this difference.

Signed-off-by: Alison Wang <b18965@freescale.com>
Acked-by: Stefano Babic <sbabic@denx.de>
Reviewed-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>