kvm/eventfd: use list_for_each_entry when deassign ioeventfd

Simpify kvm_deassign_ioeventfd_idx to use list_for_each_entry as the
loop just ends at the entry that's found and deleted.

Note, coalesced_mmio_ops and ioeventfd_ops are the only instances of
kvm_io_device_ops that implement a destructor, all other callers of
kvm_io_bus_unregister_dev() are unaffected by this change.

Suggested-by: Michal Luczaj <mhal@rbox.co>
Signed-off-by: Wei Wang <wei.w.wang@intel.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20230207123713.3905-3-wei.w.wang@intel.com
[sean: call out that only select users implement a destructor]
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: wei-w-wang

virt/kvm/eventfd.c

@@ -901,7 +901,7 @@ static int
 kvm_deassign_ioeventfd_idx(struct kvm *kvm, enum kvm_bus bus_idx,
 			   struct kvm_ioeventfd *args)
 {
-	struct _ioeventfd        *p, *tmp;
+	struct _ioeventfd        *p;
 	struct eventfd_ctx       *eventfd;
 	struct kvm_io_bus	 *bus;
 	int                       ret = -ENOENT;
@@ -915,8 +915,7 @@ kvm_deassign_ioeventfd_idx(struct kvm *kvm, enum kvm_bus bus_idx,
 
 	mutex_lock(&kvm->slots_lock);
 
-	list_for_each_entry_safe(p, tmp, &kvm->ioeventfds, list) {
-
+	list_for_each_entry(p, &kvm->ioeventfds, list) {
 		if (p->bus_idx != bus_idx ||
 		    p->eventfd != eventfd  ||
 		    p->addr != args->addr  ||