[S] Change in coreboot[main]: soc/riscv/ucb: Switch to FDT parsing to get memory size

[Maximilian Brune (Code Review)]

Attention is currently required from: Joel Bueno, Philipp Hug, ron minnich.

Maximilian Brune has posted comments on this change by Joel Bueno. ( https://review.coreboot.org/c/coreboot/+/86588?usp=email )

Change subject: soc/riscv/ucb: Switch to FDT parsing to get memory size
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Patch Set 3: Code-Review+2