sunxi: add sun7i dram setup support

sunxi: add sun7i dram setup support

This patch adds DRAM initialisation support for the Allwinner A20 (sun7i)
processor. This code will not been compiled until the build is hooked up in a
later patch. It has been split out to keep the patches manageable.

Signed-off-by: Alexandru Gagniuc <[email protected]>
Signed-off-by: Emilio López <[email protected]>
Signed-off-by: Hans de Goede <[email protected]>
Signed-off-by: Henrik Nordstrom <[email protected]>
Signed-off-by: Jens Kuske <[email protected]>
Signed-off-by: Luke Leighton <[email protected]>
Signed-off-by: Oliver Schinagl <[email protected]>
Signed-off-by: Siarhei Siamashka <[email protected]>
Signed-off-by: Stefan Roese <[email protected]>
Signed-off-by: Ian Campbell <[email protected]>
Reviewed-by: Marek Vasut <[email protected]>
Cc: Tom Cubie <[email protected]>
Reviewed-by: Tom Rini <[email protected]>