asmlinkage, kvm: Make kvm_rebooting visible

asmlinkage, kvm: Make kvm_rebooting visible

kvm_rebooting is referenced from assembler code, thus
needs to be visible.

Cc: Gleb Natapov <gleb@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1391845930-28580-1-git-send-email-ak@linux.intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
(cherry picked from commit 52480137d82062bb8d0fb778cb9934667958e367)
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>