ARM: dts: msm: Remove rpm handshake from spm sequence for sdx20

CPU spm handshakes with rpm for single cpu devices. Remove rpm
handshake by default from spm sequence. Instead it will be set
when cluster level LPM with rpm notification is selected.

Change-Id: I461644277ac2a5e7729e39ad29b2710a5376f0c3
Signed-off-by: Srinivas Rao L <lsrao@codeaurora.org>
Signed-off-by: Naresh Malladi <namall@codeaurora.org>