drm/amd/display: Disentangle dc.h include from amdgpu.h

Use forward declaration in amdgpu_dm.h for struct dc instand
of include dc.h to make header files more standalone

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h

@@ -28,7 +28,6 @@
 
 #include <drm/drmP.h>
 #include <drm/drm_atomic.h>
-#include "dc.h"
 
 /*
  * This file contains the definition for amdgpu_display_manager
@@ -53,6 +52,7 @@
 struct amdgpu_device;
 struct drm_device;
 struct amdgpu_dm_irq_handler_data;
+struct dc;
 
 struct amdgpu_dm_prev_state {
 	struct drm_framebuffer *fb;

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c

@@ -25,6 +25,7 @@
 
 #include "amdgpu_mode.h"
 #include "amdgpu_dm.h"
+#include "dc.h"
 #include "modules/color/color_gamma.h"
 
 #define MAX_DRM_LUT_VALUE 0xFFFF