ARM: dts: msm: Change GPU Bus bandwidth

Calculate GPU Bus bandwidth using oxili_ocmemgx_clk freq and DDR freq.
This fixes incorrect bandwidth caused from using ocmemcx_ocmemnoc_clk
and gcc_bimc_clk.

Change-Id: Ia286dda89d82bfe2d729b3d164a68113361829f6
Signed-off-by: Lokesh Batra <lbatra@codeaurora.org>