KVM: Provide function for VCPU lookup by id

KVM: Provide function for VCPU lookup by id

Orabug: 22623852

commit db27a7a37aa0b1f8b373f8b0fb72a2ccaafb85b7 upstream.

Let's provide a function to lookup a VCPU by id.

Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
[split patch from refactoring patch]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit af2bcce2e22c7d59816e890d67ab1af91fe0d95a)
Signed-off-by: Dan Duval <dan.duval@oracle.com>