arm64: dts: qcom: sm6115: Add RMTFS

Add a node for RMTFS and associate it with MSA and NAV IDs to enable
modem functionality on SM6115.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230406-topic-lenovo_features-v2-2-625d7cb4a944@linaro.org