sunxi: H616: DRAM: rename Kconfig parameters to be more generic

sunxi: H616: DRAM: rename Kconfig parameters to be more generic

The H616 DRAM controller requires some board specific parameters, which
we declare in Kconfig, let each board specify in their defconfig, and
then use in the DRAM init code.

Other DRAM controllers now require a very similar, if not identical
parameter set, with so far the same parameter names used.

To help keep the Kconfig file at bay, rename the existing parameter
names to drop the H616_ part in there, to make them more naturally
reusable for other SoCs.

No functional change, just a rename.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com>