eudev: fix printf usage in init script

Using a variable in a printf format string may lead to undesirable
results if the variable contains format controls, so replace

    printf "foo $var bar"

by

    printf "foo %s bar" "$var"

Signed-off-by: Carlos Santos <casantos@datacom.ind.br>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/eudev/S10udev

@@ -27,7 +27,7 @@ test -r $UDEV_CONFIG || exit 6
 
 case "$1" in
     start)
-        printf "Populating ${udev_root:-/dev} using udev: "
+        printf "Populating %s using udev: " "${udev_root:-/dev}"
         printf '\000\000\000\000' > /proc/sys/kernel/hotplug
         $UDEV_BIN -d || { echo "FAIL"; exit 1; }
         udevadm trigger --type=subsystems --action=add