dt-bindings: ufs: cdns,ufshc: add missing dma-coherent field

Add missing dma-coherent property to schema which avoids the following warnings

ufs-wrapper@4e80000: ufs@4e84000: Unevaluated properties are not allowed ('dma-coherent' was unexpected)

Signed-off-by: Matt Ranostay <mranostay@ti.com>
Link: https://lore.kernel.org/r/20221013194559.128643-1-mranostay@ti.com


Signed-off-by: Rob Herring <robh@kernel.org>