ARM: dts: msm: Add the clock OPP property for GPU clock on MSMCOBALT

The OPP table containing the frequency and voltage mappings for
the gfx3d_clk_src is used by the GPU driver for limits management
on MSMCOBALT. Enable the clock support to populate this table.

CRs-Fixed: 986567
Change-Id: I478e7e90337060e92f07e6a3ee0f7d401b796f24
Signed-off-by: Deepak Katragadda <dkatraga@codeaurora.org>