ARM: dts: msm Add support for SLPI PIL on sdm855

Add devicetree node for SLPI PIL which facilitates the loading of
SLPI firmware, authentication and bringing it out of reset.

Change-Id: I05fa1ed2bea64cb2f7e893ab66dcafd5cc725f82
Signed-off-by: Runmin Wang <runminw@codeaurora.org>