sun6i: Make dram clk and zq value Kconfig options

It turns out that there is a too large spread between boards to handle this
with a default value, turn this into Kconfig options, and set the values
the factory images are using for the Colombus and Mele_M9 boards.

Note this changes the ZQ default when not overriden through defconfig from
120 to 123, as that is what most boards seem to actually use.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>