drm/i915/dp: hide dp_to_i915() inside intel_dp.c

Now that only intel_dp.c uses dp_to_i915(), hide it there. This removes
a header dependency on to_i915().
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/e214aa6991aea4fc878b36dcd3eaece9f1fba592.1725012870.git.jani.nikula@intel.com

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

@@ -2085,8 +2085,6 @@ dp_to_lspcon(struct intel_dp *intel_dp)
 	return &dp_to_dig_port(intel_dp)->lspcon;
 }
 
-#define dp_to_i915(__intel_dp) to_i915(dp_to_dig_port(__intel_dp)->base.base.dev)
-
 static inline struct intel_digital_port *
 hdmi_to_dig_port(struct intel_hdmi *intel_hdmi)
 {

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

@@ -90,6 +90,8 @@
 #include "intel_vrr.h"
 #include "intel_crtc_state_dump.h"
 
+#define dp_to_i915(__intel_dp) to_i915(dp_to_dig_port(__intel_dp)->base.base.dev)
+
 /* DP DSC throughput values used for slice count calculations KPixels/s */
 #define DP_DSC_PEAK_PIXEL_RATE			2720000
 #define DP_DSC_MAX_ENC_THROUGHPUT_0		340000