Add the imx_rgpio2p driver for Rapid GPIO2P controllers on i.MX7ULP.
Have added all ports on RGPIO2P_0 and RGPIO2P_1.

The configurations CONFIG_IMX_RGPIO2P and CONFIG_DM_GPIO must be set
to y to enable the drivers.

To use the GPIO function, the IBE and OBE needs to set in IOMUXC.
We did not set the bits in driver, but leave them to IOMUXC settings
of the GPIO pins. User should use IMX_GPIO_NR to generate the GPIO number
for gpio APIs access.

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