VIDEO: MX5: Switch MX5 to CONFIG_VIDEO

The framebuffer driver for MX5 is based on CONFIG_LCD.
In the current implementation, there is a serious bug
because the required memory is allocated before
relocation, but the driver knows only later which is
the resolution of the display. The patch switches the driver
to CONFIG_VIDEO and the memory is allocated by the driver itself.

We also need to switch the vision2 board code and config file
in the same commit so that this commit will be bisectable.

Signed-off-by: Stefano Babic <sbabic@denx.de>
CC: Anatolij Gustschin <agust@denx.de>
Tested-by: Stefano Babic <sbabic@denx.de>
Signed-off-by: Anatolij Gustschin <agust@denx.de>