replace functions which are only available in glib-2.24

Currently the minimal supported version of glib is 2.22.
Since testing is done with a glib that claims to be 2.22, but in fact
has APIs from newer version of glib, this bug was not caught during
submit of the patch referenced below.

Replace g_realloc_n, which is available only since 2.24, with g_renew.

Fixes commit 418026ca ("util: Introduce vfio helpers")
Signed-off-by: NOlaf Hering <olaf@aepfle.de>
Reviewed-by: NThomas Huth <thuth@redhat.com>
Reviewed-by: NCornelia Huck <cohuck@redhat.com>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>
CC: qemu-stable@nongnu.org
(cherry picked from commit d29eb678)
Signed-off-by: NMichael Roth <mdroth@linux.vnet.ibm.com>

util/vfio-helpers.c

@@ -522,8 +522,7 @@ static IOVAMapping *qemu_vfio_add_mapping(QEMUVFIOState *s,
 
     assert(index >= 0);
     s->nr_mappings++;
-    s->mappings = g_realloc_n(s->mappings, sizeof(s->mappings[0]),
-                              s->nr_mappings);
+    s->mappings = g_renew(IOVAMapping, s->mappings, s->nr_mappings);
     insert = &s->mappings[index];
     shift = s->nr_mappings - index - 1;
     if (shift) {
@@ -577,8 +576,7 @@ static void qemu_vfio_undo_mapping(QEMUVFIOState *s, IOVAMapping *mapping,
     memmove(mapping, &s->mappings[index + 1],
             sizeof(s->mappings[0]) * (s->nr_mappings - index - 1));
     s->nr_mappings--;
-    s->mappings = g_realloc_n(s->mappings, sizeof(s->mappings[0]),
-                              s->nr_mappings);
+    s->mappings = g_renew(IOVAMapping, s->mappings, s->nr_mappings);
 }
 
 /* Check if the mapping list is (ascending) ordered. */