sunxi: Remove dead ifdefs in sunxi-common.h

As variables were moved to Kconfig, some of the surrounding ifdefs were
left around, even though they were empty. Clean them up.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>