msm: dcvs: rearrange platform data

This change
-removes the use of group id and instead introduces core type
-rearranges platform data, adds energy curve coefficients and power
 parameters
-allow for the energy params to be -ve numbers

The change also mandates updates to the msm8974-gpu.dtsi and the
associated binding documentation.

Also take this opportunity to remove devices for unsupported platform
- 8930 and 8960

Change-Id: Ie8d5a691defb825955b240c1b304e04f0a21499a
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>