drm/amdgpu/vcn2.0: fix no previous prototype for functions

Include header file vcn_v2_0.h
Signed-off-by: James Zhu <James.Zhu@amd.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/vcn_v2_0.c

@@ -30,6 +30,7 @@
 #include "amdgpu_pm.h"
 #include "amdgpu_psp.h"
 #include "mmsch_v2_0.h"
+#include "vcn_v2_0.h"
 
 #include "vcn/vcn_2_0_0_offset.h"
 #include "vcn/vcn_2_0_0_sh_mask.h"