[Intel-gfx] 3 duplicate register #defines in i915_reg.h

[Cui, Dexuan]

Hi, I found the below 3 ones:
PFIT_VERT_SCALE_MASK
PFIT_HORIZ_SCALE_MASK
TRANS_DP_AUDIO_ONLY

Maybe somebody can help to clean this up. :-)

Thanks,
-- Dexuan