KVM: s390: announce irqfd capability

s390 has acquired irqfd support with commit "KVM: s390: irq routing for
adapter interrupts" (84223598778ba08041f4297fda485df83414d57e) but
failed to announce it. Let's fix that.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

Documentation/virtual/kvm/api.txt

@@ -2126,7 +2126,7 @@ into the hash PTE second double word).
 4.75 KVM_IRQFD
 
 Capability: KVM_CAP_IRQFD
-Architectures: x86
+Architectures: x86 s390
 Type: vm ioctl
 Parameters: struct kvm_irqfd (in)
 Returns: 0 on success, -1 on error

arch/s390/kvm/kvm-s390.c

@@ -158,6 +158,7 @@ int kvm_dev_ioctl_check_extension(long ext)
 	case KVM_CAP_ONE_REG:
 	case KVM_CAP_ENABLE_CAP:
 	case KVM_CAP_S390_CSS_SUPPORT:
+	case KVM_CAP_IRQFD:
 	case KVM_CAP_IOEVENTFD:
 	case KVM_CAP_DEVICE_CTRL:
 	case KVM_CAP_ENABLE_CAP_VM: