[S390] dasd: sync after async probe

Some functions called as a late_initcall depend on completely
initialized devices. Since commit
f3445a1a

 the dasd driver uses the
new async framework and relies on the fact that synchronization is
done in prepare_namespace which is called after the late_initcalls.

Fix this by calling async_synchronize_full at the end of the related
init functions.

Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>