Consistent function style

src/freedombone-image-customise

@@ -143,11 +143,11 @@ BMX7_COMMIT='0a82c7c10fef44b259b35e77ab33632aa132d219'
 
 PATH=/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin
 
-function configure_backports {
+configure_backports() {
     echo "deb http://${DEBIAN_REPO}/debian/ ${DEBIAN_VERSION}-backports main" >> "$rootdir/etc/apt/sources.list"
 }
 
-function configure_contrib_repo {
+configure_contrib_repo() {
     if ! grep -q "contrib" "$rootdir/etc/apt/sources.list"; then
         chroot "$rootdir" /bin/sed -i "s| main| main contrib|g" /etc/apt/sources.list
     fi