update-kernel: fix "find: unpaired '('"

fixes #5883

update-kernel.in

@@ -240,7 +240,7 @@ if [ "$ARM" ]; then
     DTBDIR=$ROOT/usr/lib/linux-$KVER
     [ "$BUILDDIR" ] && DTBDIR=$BUILDDIR/source/arch/arm/boot/dts
     cp -a "$DTBDIR"/* $DTB_STAGING
-    find "$DTB_STAGING" -type f \! \( -name "*.dtb" -o -name "*.dtbo"\)  -delete
+    find "$DTB_STAGING" -type f \! \( -name "*.dtb" -o -name "*.dtbo" \)  -delete
 fi