riscv: acpi: avoid errors caused by probing DT devices when ACPI is used

Similar to the ARM64 commit 3505f30fb6a9s ("ARM64 / ACPI: If we chose
to boot from acpi then disable FDT"), let's not do DT hardware probing
if ACPI is enabled in early boot.  This avoids errors caused by
repeated driver probing.

Signed-off-by: Han Gao <rabenda.cn@gmail.com>
Link: https://lore.kernel.org/r/20250910112401.552987-1-rabenda.cn@gmail.com


[pjw@kernel.org: cleaned up patch description and subject]
Signed-off-by: Paul Walmsley <pjw@kernel.org>