arm64: dts: qcom: msm8996-xiaomi-*: Enable MSS and SLPI

Enable mss_pil and slpi_pil and set their firmware paths.

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/20210926190555.278589-6-y.oudjana@protonmail.com