imx: mx7ulp: add iomux driver to support IOMUXC0 and IOMUXC1

Add a new driver under ULP directory to support its IOMUXC
controllers. The ULP has two IOMUXC, the IOMUXC0 is used
for M4 domain, while IOMUXC1 is for A7. We set IOMUXC1 as
the default IOMUX in this driver. Any pins in IOMUXC0 needs
to configure with IOMUX_CONFIG_MPORTS in its mux_mode field.

Signed-off-by: Ye Li <ye.li@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by : Stefano Babic <sbabic@denx.de>