qapi: Use QAPI_LIST_APPEND in trivial cases

The easiest spots to use QAPI_LIST_APPEND are where we already have an
obvious pointer to the tail of a list.  While at it, consistently use
the variable name 'tail' for that purpose.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20210113221013.390592-5-eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
diff --git a/qga/commands-win32.c b/qga/commands-win32.c
index 684639b..a6cc481 100644
--- a/qga/commands-win32.c
+++ b/qga/commands-win32.c
@@ -1833,7 +1833,7 @@
 {
     PSYSTEM_LOGICAL_PROCESSOR_INFORMATION pslpi, ptr;
     DWORD length;
-    GuestLogicalProcessorList *head, **link;
+    GuestLogicalProcessorList *head, **tail;
     Error *local_err = NULL;
     int64_t current;
 
@@ -1841,7 +1841,7 @@
     length = 0;
     current = 0;
     head = NULL;
-    link = &head;
+    tail = &head;
 
     if ((GetLogicalProcessorInformation(pslpi, &length) == FALSE) &&
         (GetLastError() == ERROR_INSUFFICIENT_BUFFER) &&
@@ -1864,18 +1864,13 @@
             while (cpu_bits > 0) {
                 if (!!(cpu_bits & 1)) {
                     GuestLogicalProcessor *vcpu;
-                    GuestLogicalProcessorList *entry;
 
                     vcpu = g_malloc0(sizeof *vcpu);
                     vcpu->logical_id = current++;
                     vcpu->online = true;
                     vcpu->has_can_offline = true;
 
-                    entry = g_malloc0(sizeof *entry);
-                    entry->value = vcpu;
-
-                    *link = entry;
-                    link = &entry->next;
+                    QAPI_LIST_APPEND(tail, vcpu);
                 }
                 cpu_bits >>= 1;
             }