kvm: add kvm_{vm,vcpu}_enable_cap
Provide helper functions for enabling capabilities (on a vcpu and on a vm).
Reviewed-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Reviewed-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>