nios2: convert nios2 cpu to driver model

Convert nios2 cpu to driver model. The cpu parameters are
extracted from device tree and saved to global data structure.
We will use them to replace the custom_fpga.h .

Signed-off-by: Thomas Chou <thomas@wytron.com.tw>
Reviewed-by: Simon Glass <sjg@chromium.org>
5 files changed