ARM: sunxi: dt: build DTs according to new MACH_SUNxI Kconfig symbols

Allwinner sunxi support has been split into the various SoCs in Kconfig.
Adapt the new symbols for the device trees.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>