iommu: Improve client fault handling

On some platforms, certain IOMMU hardware state
might be cleared before reaching client fault handlers,
making it difficult for client fault handlers to do much
useful processing. Add some flags so that this information
can be passed to client fault handlers directly, rather
than expecting clients to read the hardware themselves.

Also provide a mechanism for client fault handlers to
request that the IOMMU driver not clear the fault or
resume/retry the faulting transaction. The client fault
handler can return -EBUSY to request this behavior.

Change-Id: I9780beb52b4257fff99d708a493173c9fe0a9d8a
Signed-off-by: Sushmita Susheelendra <ssusheel@codeaurora.org>