drm/amd/display: Don't ASSERT when total_planes == AMDGPU_MAX_PLANES

[Why]
Can happen on ASICs with 6 planes, but this isn't a bug since we haven't
written outside the array.

[How]
Use <= instead of <.

Cc: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reported-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Tested-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -1915,7 +1915,7 @@ static int amdgpu_dm_initialize_drm_device(struct amdgpu_device *adev)
 	primary_planes = dm->dc->caps.max_streams;
 
 	total_planes = primary_planes + overlay_planes;
-	ASSERT(total_planes < AMDGPU_MAX_PLANES);
+	ASSERT(total_planes <= AMDGPU_MAX_PLANES);
 
 	/*
 	 * Initialize primary planes, implicit planes for legacy IOCTLS.