brcm2708: fix early bootloader config restore

Restoring the bootloader config before rebooting fails:
tar: invalid tar magic

Add the -z option to the tar command to fix this.

Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>

target/linux/brcm2708/base-files/lib/upgrade/platform.sh

@@ -97,7 +97,7 @@ platform_copy_config() {
 		mkdir -p /boot
 		[ -f /boot/kernel.img ] || mount -t vfat -o rw,noatime "/dev/$partdev" /boot
 		cp -af "$CONF_TAR" /boot/
-		tar -C / -xvf "$CONF_TAR" boot/config.txt
+		tar -C / -zxvf "$CONF_TAR" boot/config.txt
 		sync
 		unmount /boot
 	fi