As DT support for clocks and smp_twd is enabled, add clock entry
for smp_twd clock to DT.

This fixes the following error while booting the kernel:
smp_twd: clock not found -2
Signed-off-by: Prashant Gaikwad <pgaikwad@nvidia.com>
[swarren: include kernel log spew that this fixes]
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Olof Johansson <olof@lixom.net>