ARM: dts: msm: Add GDSC and dummy clocks support for SDM640

Add dummy clock device nodes for all clock controllers present on SDM640.
Also add the required GDSCs present on SDM640 and enable them for the
clients to be able to request for the phandle.

Change-Id: I2e9b87b6497162bbaa27dd04f832c5cb6533ab8a
Signed-off-by: Amit Nischal <anischal@codeaurora.org>