Clarify the allocation/free recommendations; this is mostly
just tidying up following the global-search-and-replace done
with the conversion to the GLib g_malloc and friends.
Reviewed-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>