ARM: imx: vining2000: Convert to SPL framework

In preparation for use of DDR DRAM fine-tuning upon boot,
convert the board to SPL framework instead of using DCD
tables to bring up DRAM and pinmux.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Cc: Silvio Fricke <silvio.fricke@softing.com>
Cc: Stefano Babic <sbabic@denx.de>