Impact: build/boot fix for x86/Voyager

This change:

| commit 3d442233
| Author: Jens Axboe <jens.axboe@oracle.com>
| Date:   Thu Jun 26 11:21:34 2008 +0200
|
|     Add generic helpers for arch IPI function calls

didn't wire up the voyager smp call function correctly, so do that
here.  Also make CONFIG_USE_GENERIC_SMP_HELPERS a def_bool y again,
since we now use the generic helpers for every x86 architecture.
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Jens Axboe <Jens.Axboe@oracle.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>