LoongArch: Provisionally add ACPICA data structures

The LoongArch architecture is using ACPI, but the spec containing
the required updates still is in an unreleased state.

Instead of preventing the inclusion of the IRQ support into the
kernel, add the missing bits to the arch-specific parts of
the ACPICA support.

Once the ACPICA bits are updated to the version that supports
LoongArch, these bits can eventually be removed.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Jianmin Lv <lvjianmin@loongson.cn>
Link: https://lore.kernel.org/r/1658314292-35346-2-git-send-email-lvjianmin@loongson.cn