sparc64: Fix bootup crash on sun4v.

commit 9e0daff30fd7ecf698e5d20b0fa7f851e427cca5 upstream.

The DS driver registers as a subsys_initcall() but this can be too
early, in particular this risks registering before we've had a chance
to allocate and setup module_kset in kernel/params.c which is
performed also as a subsyts_initcall().

Register DS using device_initcall() insteal.

Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>