ARM: imx: Decouple mccmon6's SPL and u-boot proper code
The mccmon6 has been used a "mixed" approach between SPL and
U-Boot proper sources.
This commit decoupes SPL and u-boot proper, which allows clear
distinction between those two code bases and facilitates
conversion to DM/DTS on this particular board.
Signed-off-by:
Lukasz Majewski <lukma@denx.de>