arm64: dts: qcom: sm8550: Add dma-coherent property

Add dma-coherent property to fastRPC context bank nodes to pass dma
sequence test in fastrpc sanity test, ensure that data integrity is
maintained during DMA operations.

Signed-off-by: Ling Xu <quic_lxu5@quicinc.com>
Link: https://lore.kernel.org/r/20240125102413.3016-2-quic_lxu5@quicinc.com


Signed-off-by: Bjorn Andersson <andersson@kernel.org>