drm/i915: Clear the dpll_hw_state when disabling a pipe

Clear the dpll_hw_state when we're about disable the pipe.
Previously it looks like we just left the old junk in there.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220325123205.22140-8-ville.syrjala@linux.intel.comReviewed-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/display/intel_dpll.c

@@ -1406,12 +1406,12 @@ int intel_dpll_crtc_compute_clock(struct intel_atomic_state *state,
 	if (drm_WARN_ON(&i915->drm, crtc_state->shared_dpll))
 		return 0;
 
-	if (!crtc_state->hw.enable)
-		return 0;
-
 	memset(&crtc_state->dpll_hw_state, 0,
 	       sizeof(crtc_state->dpll_hw_state));
 
+	if (!crtc_state->hw.enable)
+		return 0;
+
 	return i915->dpll_funcs->crtc_compute_clock(state, crtc);
 }