replace functions which are only available in glib-2.24

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 418026ca43 ("util: Introduce vfio helpers")

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
CC: qemu-stable@nongnu.org
(cherry picked from commit d29eb678bcfbb2fbf4b79423797253ee02f5c6cf)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>