msm: kgsl: Read speed bin information from device tree

Speed bin information is sometimes written to efuses to
specify a GPU frequency plan available on a platform. The
current code only supports reading the efuses for msm8996v3.
Hence specify it in the platform device tree node to
support multiple platforms.

CRs-Fixed: 967494
Change-Id: I5db4d5a35e2700250517ea6cac3d4d736936ce9f
Signed-off-by: Suman Tatiraju <sumant@codeaurora.org>