ARM: mach-ux500: use SGI0 to wake up the other core

The commit 7d28e3ea
("ARM: ux500: wake secondary cpu via resched") makes use
of schedule IPI to wake up the secondary core which seems
incorrect. Rather use SGI0.

Signed-off-by: srinidhi kasagar <srinidhi.kasagar@stericsson.com>
Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Acked-by: Olof Johansson <olof@lixom.net>