Update platform.c to drop unnecessary K230 specific operations

[yf13]

PR描述:

U-Boot already has K230 specific operations, this operation is unnecessary. We can drop this to be closer with mainline OpenSBI.

详细描述:

This is duplicated with operations src/little/uboot/arch/riscv/cpu/k230/cpu.c:harts_early_init().

关联issue:

None

[wuwentao]

merged, thank you very much for your PR. it will be rebase in our main branch.