ARM: dts: msm: Add S2 and S6 RPM floor corner regulators for APQ8084

Add RPM floor corner regulator device nodes for S2
and S6 regulators, which control the VDD_CX and
VDD_GFX rails. These regulator device nodes are
required to limit the regulator voltage and the
operating mode of the rails, during certain
temperatures.

Change-Id: I25fe6d7118c992db2ae509b727ce734e3c03c75d
Signed-off-by: Ram Chandrasekar <rkumbako@codeaurora.org>