[ALPS08693813] Fix boot performance fail issue

1. Fix gpueb sysram last commit index value uninitialized issue
that causes MFG restore last frequency as max frequency when GPU
power on.
2. Skip DVFS when current FPS < 20(Only on boot time).

MTK-Commit-Id: 93a12e333a5be62dc0a9d3cae3441fdbeea74061

CR-Id: ALPS08693813
Feature: GED driver
Change-Id: I580880a9d360a69dd0718c55864bd2a4f8779b4d
Signed-off-by: Knight Weng <knight.weng@mediatek.com>