of: property: Add device link support for "iommu-map"

of: property: Add device link support for "iommu-map"

Commit 8e12257dead7 ("of: property: Add device link support for iommus,
mboxes and io-channels") added device link support for IOMMU linkages
described using the "iommus" property. For PCI devices, this property
is not present and instead the "iommu-map" property is used on the host
bridge node to map the endpoint RequesterIDs to their corresponding
IOMMU instance.

Add support for "iommu-map" to the device link supplier bindings so that
probing of PCI devices can be deferred until after the IOMMU is
available.

Cc: Rob Herring <robh@kernel.org>
Cc: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
Acked-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20191120190028.4722-1-will@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>