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 <ats@offog.org>
Signed-off-by: Aleksei Mamlin <mamlinav@gmail.com>
Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Emilio López <emilio@elopez.com.ar>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Henrik Nordstrom <henrik@henriknordstrom.net>
Signed-off-by: Jens Kuske <jenskuske@gmail.com>
Signed-off-by: Luc Verhaegen <libv@skynet.be>
Signed-off-by: Luke Leighton <lkcl@lkcl.net>
Signed-off-by: Oliver Schinagl <oliver@schinagl.nl>
Signed-off-by: Patrick Wood <patrickhwood@gmail.com>
Signed-off-by: Stefan Roese <sr@denx.de>
Signed-off-by: Wills Wang <wills.wang.open@gmail.com>
Signed-off-by: Ian Campbell <ijc@hellion.org.uk>
Reviewed-by: Marek Vasut <marex@denx.de>
Cc: Tom Cubie <Mr.hipboi@gmail.com>
Reviewed-by: Tom Rini <trini@ti.com>