Oldland: move malloc heap to the top of memory.

This frees the lower area of SDRAM for booting something else.

Signed-off-by: Jamie Iles <jamie@jamieiles.com>
Oldland: fix timer counting direction to match hardware.

Signed-off-by: Jamie Iles <jamie@jamieiles.com>
Oldland: enable memory testing.

Signed-off-by: Jamie Iles <jamie@jamieiles.com>