drm/amdgpu: use defines for CRTCs and AMFT blocks

Prerequiste for the next patch which ups the limits.
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h

@@ -309,8 +309,8 @@ struct amdgpu_mode_info {
 	struct atom_context *atom_context;
 	struct card_info *atom_card_info;
 	bool mode_config_initialized;
-	struct amdgpu_crtc *crtcs[6];
-	struct amdgpu_afmt *afmt[7];
+	struct amdgpu_crtc *crtcs[AMDGPU_MAX_CRTCS];
+	struct amdgpu_afmt *afmt[AMDGPU_MAX_AFMT_BLOCKS];
 	/* DVI-I properties */
 	struct drm_property *coherent_mode_property;
 	/* DAC enable load detect */