sunxi: add sun7i cpu, board and start of day support

sunxi: add sun7i cpu, board and start of day support

This patch adds generic board, start of day and basic build system 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: Adam Sampson <[email protected]>
Signed-off-by: Aleksei Mamlin <[email protected]>
Signed-off-by: Alexandru Gagniuc <[email protected]>
Signed-off-by: Chen-Yu Tsai <[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: Luc Verhaegen <[email protected]>
Signed-off-by: Luke Leighton <[email protected]>
Signed-off-by: Oliver Schinagl <[email protected]>
Signed-off-by: Patrick Wood <[email protected]>
Signed-off-by: Stefan Roese <[email protected]>
Signed-off-by: Wills Wang <[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]>