arm64: dts: qcom: sm6375: Add RMTFS

Add a node for RMTFS on SM6375.

Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230213175928.1979637-1-konrad.dybcio@linaro.org