dt-bindings: arm-smmu: Add compatible for the SDX55 SoC

Add missing compatible for the SDX55 SoC.

Signed-off-by: David Heidelberg <david@ixit.cz>
Link: https://lore.kernel.org/r/20211020231701.278846-1-david@ixit.cz


Signed-off-by: Will Deacon <will@kernel.org>