rockchip: sdram: Update the driver to support of-platdata

rockchip: sdram: Update the driver to support of-platdata

Add support for of-platdata with rk3288 SDRAM initr. This requires decoding
the of-platdata struct and setting up the device from that. Also the driver
needs to be renamed to match the string that of-platdata will search for.

The platform data is copied from the of-platdata structure to the one used
by the driver. This allows the same code to be used with device tree and
of-platdata.

Signed-off-by: Simon Glass <sjg@chromium.org>