drm/amdgpu: correct hbm field in boot status

hbm filed takes bit 13 and bit 14 in boot status.

Signed-off-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Tao Zhou <tao.zhou1@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>