sunxi: build both sunxi core.c and sun7i core.c

fold sun7i memory.h and timex.h into sunxi

Signed-off-by: Michal Suchanek <hramrach@gmail.com>
sun7i: remove files that are identical in plat-sunxi

Signed-off-by: Michal Suchanek <hramrach@gmail.com>
Import sun7i nand driver - wip