sunxi: Update sunxi-common.h to deal with different A1-SRAM base addr on sun9i

sunxi: Update sunxi-common.h to deal with different A1-SRAM base addr on sun9i

The A1 SRAM Base differs between sun9i and the others, update sunxi-common.h
to deal with this, so that we do not set the initial stack pointer to point
to the BROM.

This avoids the need for the weird undocumented register write I previously
took from the allwiner u-boot sources and which needed #ifdef-ery in start.S
as it needed to be done really early on.

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