We had an unwritten rule about declarations having to be at beginning of
blocks. Make it a written rule.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: Stefan Weil <sw@weilnetz.de>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>