arm: sunxi: Allow per-platform DRAM ZQ configuration on sun8i

arm: sunxi: Allow per-platform DRAM ZQ configuration on sun8i

A few sun8i platforms define specific default DRAM ZQ values, but they
are not taken in account because of MACH_SUN8I being used for the 123
default first.

Replace MACH_SUN8I with the list of platforms that don't have specific
DRAM ZQ values, to avoid overwriting the default for those that do.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Acked-by: Jagan Teki <jagan@openedev.com>