neek: add LCD controller

Add vga_lcd core and connect it to the ddr controller.

To make it work at 800x600x24bpp @60Hz, changed the ddr
controller BUF_WIDTH to 5 (32 bytes buffer).

Make changes in ddr_ctrl_wrapper.v, wb_port.v, dpram_altera.v
and wb_ddr_ctrl.v to make BUF_WIDTH=5 work.

Change the wb_clk to 75MHz.