board: verdin-imx8mp: update ddrc config for different lpddr4 memories

Add support to Verdin IMX8MP V1.1B SKU which uses
MT53E1G32D2FW-046 WT:B memory.
Compared to the 8 GB memory (MT53E2G32D4NQ-046 WT:A) used on
Verdin IMX8MP V1.0A it has 16 row addresses instead of 17.
In fact, the new memory, is a 2 GB/rank memory. The 8 GB memory is a
4 GB/rank memory.

Manually tweaking Host Interface addresses vs LPDDR4 signals mapping it
is possible to have a single configuration working with both memories:
 - Old configuration: HIF bit 30 -> rank, HIF bit 29 -> Row 16
 - New configuration: HIF bit 29 -> rank, HIF bit 30 -> Row 16

With this change the memory space from the host processor is contiguous
for both the configurations and the correct memory size is computed
using get_ram_size() at runtime.

Support for single rank memories still works thanks to the fact
dual ranks training fails (ddr_init->ddr_cfg_phy) toward single rank
memories.

Signed-off-by: Emanuele Ghidoli <emanuele.ghidoli@toradex.com>
Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>