KVM guest: Fix section mismatch derived from kvm_guest_cpu_online()

WARNING: arch/x86/built-in.o(.text+0x1bb74): Section mismatch in reference from the function kvm_guest_cpu_online() to the function .cpuinit.text:kvm_guest_cpu_init()
The function kvm_guest_cpu_online() references
the function __cpuinit kvm_guest_cpu_init().
This is often because kvm_guest_cpu_online lacks a __cpuinit
annotation or the annotation of kvm_guest_cpu_init is wrong.

This patch fixes the warning.

Tested with linux-next (next-20101231)

Signed-off-by: Sedat Dilek <sedat.dilek@gmail.com>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>