drm/amdgpu: Fix logic error

This commit fixes logic error in function 'amdgpu_hw_ip_info':
       - value 'uvd' might be 'vcn'.

Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>