[PATCH] x86_64/ia64 : Fix compilation error for node_to_first_cpu

Fixes a compiler error in node_to_first_cpu, __ffs expects unsigned long as
a parameter; instead cpumask_t was being passed.  The macro
node_to_first_cpu was not yet used in x86_64 and ia64 arches, and so we never
hit this.  This patch replaces __ffs with first_cpu macro, similar to other
arches.

Signed-off-by: Alok N Kataria <alokk@calsoftinc.com>
Signed-off-by: Ravikiran G Thirumalai <kiran@scalex86.org>
Signed-off-by: Shai Fultheim <shai@scalex86.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>