drm/amdgpu/vpe: fix truncation warnings

Fix truncation warnings.

Fixes: 9d4346bd ("drm/amdgpu: add VPE 6.1.0 support")
Signed-off-by: Lang Yu <Lang.Yu@amd.com>
Reviewed-by: Yifan Zhang <yifan1.zhang@amd.com>
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/oe-kbuild-all/202309200028.aUVuM8os-lkp@intel.com


Signed-off-by: Alex Deucher <alexander.deucher@amd.com>