arm64: dts: qcom: msm8996: Add MSS and SLPI

Add nodes for the MSS and SLPI remoteprocs.

Signed-off-by: Yassine Oudjana <y.oudjana@protonmail.com>
Tested-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> #db820c
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20210926190555.278589-5-y.oudjana@protonmail.com