ARM: sunxi: Add missing sun4i.dtsi file

Patch f055f1f6 [ARM: sunxi: Add sun4i and cubieboard support] missed
this sun4i.dtsi include file. This patch finally brings it upstream
enabling support for sun4i boards.

Signed-off-by: Stefan Roese <sr@denx.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Maxime Ripard <maxime.ripard@free-electrons.com>