iommu/arm-smmu: add option to skip SMR mask sanity check

Usually when an SMMU probes we do a sanity check on the SMR registers to
make sure they can fully support all of the mask bits.  This check can
cause problems for use cases where the SMMU is already in use when the
SMMU probes.  For example, for continuous splash screen support, the
stream matching table is programmed before control is even turned over
to Linux.

Add an option to skip this sanity check.

Change-Id: I51a9231fcd8b73034f1a1ca69e4fbb7e632635fa
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>