dtrace: zero-initialize the fake vmlinux module's pdata space

dtrace: zero-initialize the fake vmlinux module's pdata space

We need to do this because we bypass normal module initialization for this
"module", so move_module() is never called for it and the memory is never zeroed
as it is for real modules.

If this is not done, we end up with a non-initialized pdata which may contain
e.g. a non-zero count of the number of registered SDT probes, even before any
had been registered.  (This would have the effect of preventing the registration
of any SDT probes in the main kernel, forever.)

Orabug: 19005031
Signed-off-by: Nick Alcock <nick.alcock@oracle.com>
Reviewed-by: Kris Van Hees <kris.van.hees@oracle.com>