drm/radeon: drop dce6_dp_enable

It's mostly duplicated with evergreen_dp_enable. This
is a prerequisite for fix implemented in another patch.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
diff --git a/drivers/gpu/drm/radeon/radeon_audio.c b/drivers/gpu/drm/radeon/radeon_audio.c
index 48d49e6..2c17df9 100644
--- a/drivers/gpu/drm/radeon/radeon_audio.c
+++ b/drivers/gpu/drm/radeon/radeon_audio.c
@@ -102,7 +102,6 @@
 void r600_hdmi_enable(struct drm_encoder *encoder, bool enable);
 void evergreen_hdmi_enable(struct drm_encoder *encoder, bool enable);
 void evergreen_dp_enable(struct drm_encoder *encoder, bool enable);
-void dce6_dp_enable(struct drm_encoder *encoder, bool enable);
 
 static const u32 pin_offsets[7] =
 {
@@ -240,7 +239,7 @@
 	.set_avi_packet = evergreen_set_avi_packet,
 	.set_audio_packet = dce4_set_audio_packet,
 	.mode_set = radeon_audio_dp_mode_set,
-	.dpms = dce6_dp_enable,
+	.dpms = evergreen_dp_enable,
 };
 
 static void radeon_audio_interface_init(struct radeon_device *rdev)