turris-nor-update: fix exit if not running on BTRFS

The result without argument returns $? and thus 1 that triggers error
and termination of nor-update. The zero has to be returned explicitly
there.

hardware/turris-nor-update/Makefile

@@ -8,8 +8,8 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=turris-nor-update
-PKG_VERSION:=1.0.1
-PKG_RELEASE:=2
+PKG_VERSION:=1.0.2
+PKG_RELEASE:=1
 
 PKG_MAINTAINER:=CZ.NIC <packaging@turris.cz>
 

hardware/turris-nor-update/files/nor-update

@@ -99,7 +99,7 @@ boot_scr_cleanup() {
 fix_boot_scr() (
     local dev="$(sed -n 's|^\(/dev/[a-z0-9]*\) / btrfs .*|\1|p' /proc/mounts)"
     # Fix is required only for BTRFS. No need to continue if root filesystem is not BTRFS.
-    [ -n "$dev" ] || return
+    [ -n "$dev" ] || return 0
     tmpdir="$(mktemp -d)"
     [ -n "$tmpdir" ] || die "Can't create a temp directory!"
     trap boot_scr_cleanup EXIT