FIXED103: basic OC/UV tweaks (based on latest infernal-k99 3.0.8)

+ revert/fix a few defconfig items
+ add k99 basic CPU OC/UV: lowest CPU freq to 192MHz, max-OC to 1674MHz
  (based on my own infernal-K99 tweaks)
+ add k99 basic GPU OC: 2D-max 320MHz@400BUS & 3D-max 450MHz@533BUS
  (likewise based on my own infernal-K99 tweaks)