drm/i915: Remove prototype for intel_cx0_phy_ddi_vswing_sequence()

That function is not defined anywhere.
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
Reviewed-by: Ravi Kumar Vodapalli <ravi.kumar.vodapalli@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230613214658.1099759-1-gustavo.sousa@intel.com

drivers/gpu/drm/i915/display/intel_cx0_phy.h

@@ -43,8 +43,5 @@ int intel_c20pll_calc_port_clock(struct intel_encoder *encoder,
 void intel_cx0_phy_set_signal_levels(struct intel_encoder *encoder,
 				     const struct intel_crtc_state *crtc_state);
 int intel_cx0_phy_check_hdmi_link_rate(struct intel_hdmi *hdmi, int clock);
-void intel_cx0_phy_ddi_vswing_sequence(struct intel_encoder *encoder,
-				       const struct intel_crtc_state *crtc_state,
-				       u32 level);
 int intel_mtl_tbt_calc_port_clock(struct intel_encoder *encoder);
 #endif /* __INTEL_CX0_PHY_H__ */