drm/i915: Remove the PS_PWR_GATE write from skl_program_scaler()

If we don't need the PS_PWR_GATE write when programming the
pipe scaler I don't see why we'd need it for plane scalers either.
Just remove it.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181101150605.18235-4-ville.syrjala@linux.intel.comReviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/i915/intel_sprite.c

@@ -347,7 +347,6 @@ skl_program_scaler(struct intel_plane *plane,
 
 	I915_WRITE_FW(SKL_PS_CTRL(pipe, scaler_id),
 		      PS_SCALER_EN | PS_PLANE_SEL(plane->id) | scaler->mode);
-	I915_WRITE_FW(SKL_PS_PWR_GATE(pipe, scaler_id), 0);
 	I915_WRITE_FW(SKL_PS_VPHASE(pipe, scaler_id),
 		      PS_Y_PHASE(y_vphase) | PS_UV_RGB_PHASE(uv_rgb_vphase));
 	I915_WRITE_FW(SKL_PS_HPHASE(pipe, scaler_id),