parisc/CPU hotplug: Add missing call to notify_cpu_starting()

The scheduler depends on receiving the CPU_STARTING notification, without
which we end up into a lot of trouble. So add the missing call to
notify_cpu_starting() in the bringup code.

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-and-Tested-by: Mikulas Patocka <mpatocka@redhat.com>
Acked-and-Tested-by: Tobias Ulmer <tobiasu@tmux.org>
Tested-by: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>