KVM: x86/xen: Remove extra unlock in kvm_xen_hvm_set_attr()

This accidentally ended up locking and then immediately unlocking kvm->lock
at the beginning of the function. Fix it.

Fixes: a76b9641 ("KVM: x86/xen: add KVM_XEN_HVM_SET_ATTR/KVM_XEN_HVM_GET_ATTR")
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Message-Id: <20210208232326.1830370-2-dwmw2@infradead.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/xen.c

@@ -105,8 +105,6 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
 
 	mutex_lock(&kvm->lock);
 
-	mutex_unlock(&kvm->lock);
-
 	switch (data->type) {
 	case KVM_XEN_ATTR_TYPE_LONG_MODE:
 		if (!IS_ENABLED(CONFIG_64BIT) && data->u.long_mode) {