riscv: errata: thead: only set cbom size & noncoherent during boot

The CBOM size and whether the HW is noncoherent is known and
determined during booting and won't change after that.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230614165504.532-2-jszhang@kernel.org


Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>