sunxi: H6/H616: dram: remove usage of struct sunxi_prcm_reg

sunxi: H6/H616: dram: remove usage of struct sunxi_prcm_reg

The Allwinner H6 and H616 DRAM initialisation code uses a complex C
struct, modelling the PRCM clock register frame. For those SoCs, this
struct contains 20 registers, but the DRAM code only uses two of them.

Since we want to get rid of this struct, drop the usage of the struct in
the H6 and H616 DRAM code, by using #define'd register names and their
offset, and then adding those names to the base pointer.

This removes one more user of the PRCM clock register struct.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>