ram: k3-am654: Do not rely on default values for certain DDR register

Added the following registers to the DDR configuration:
- ACIOCR0,
- ACIOCR3,
- V2H_CTL_REG,
- DX8SLxDQSCTL.

Modified enable_dqs_pd and disable_dqs_pd to only touch the associated
bit fields for pullup and pulldown registers (to preserve slew rate and
other bits in that same register). Also update the dts files in the same
patch to maintain git bisectability.

Signed-off-by: James Doublesin <doublesin@ti.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>