iommu/riscv: Empty iommu queue before enabling it

Changing cqen/fqen/pqen from 0 to 1 sets the cqh/fqt/pqt registers to 0.
But the cqt/fqh/pqh registers are left unmodified. This commit resets
cqt/fqh/pqh registers to ensure corresponding queues are empty before
being enabled during initialization.

Signed-off-by: Xu Lu <luxu.kernel@bytedance.com>
Link: https://lore.kernel.org/r/20250103093220.38106-2-luxu.kernel@bytedance.com


Signed-off-by: Joerg Roedel <jroedel@suse.de>