sunxi: Convert sun5i boards to use auto dram configuration

Currently we've separate detailed dram settings for all sun5i boards, this
moves them over to using auto dram configuration so that we can get rid of
all the per board dram_foo.c files.

This has been tested on a A10s-Olinuxino, A13-Olinuxino, A13-OlinuxinoM,
mk802-a10s and r7-tv-dongle board.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>