iommu: Delete iommu_dma_free_cpu_cached_iovas()

Function iommu_dma_free_cpu_cached_iovas() no longer has any caller, so
delete it.

With that, function free_cpu_cached_iovas() may be made static.

Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/1616675401-151997-4-git-send-email-john.garry@huawei.com


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