KVM: add kvm_{test,clear}_request to replace {test,clear}_bit

Users were expected to use kvm_check_request() for testing and clearing,
but request have expanded their use since then and some users want to
only test or do a faster clear.

Make sure that requests are not directly accessed with bit operations.

Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/s390/kvm/kvm-s390.c

@@ -2496,7 +2496,7 @@ retry:
 	}
 
 	/* nothing to do, just clear the request */
-	clear_bit(KVM_REQ_UNHALT, &vcpu->requests);
+	kvm_clear_request(KVM_REQ_UNHALT, vcpu);
 
 	return 0;
 }