sunxi: Add a33 dram init code

Based on Allwinner dram init code from the a33 bsp:
https://github.com/allwinner-zh/bootloader/blob/master/basic_loader/bsp/bsp_for_a33/init_dram/mctl_hal.c



Initial u-boot port by Vishnu Patekar, major cleanup / rewrite by
Hans de Goede.

Signed-off-by: Vishnu Patekar <vishnupatekar0510@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>