imx: mx6 sabreauto: Add board support for USB EHCI

On mx6 sabreauto board, there are two USB ports:
0: OTG
1: HOST
The EHCI driver is enabled for this board, but the IOMUX and VBUS power
control is not implemented, which cause both USB port failed to work.
This patch fix the problem by adding the board support codes.

Since the power control uses the GPIO pin from port expander MAX7310,
the PCA953X driver is enabled for accessing the MAX7310.

The ID pin of OTG Port needs to configure the GPR1 bit 13 for selecting
its daisy chain. Add a new function "imx_iomux_set_gpr_register" to
handle GPR register setting.

Signed-off-by: Ye.Li <B37916@freescale.com>