[][Add etc/wireless folder to system config backup folder]

[Description]
Add etc/wireless folder to system config backup folder

[Release-log]
N/A

Change-Id: I4514075a559508bd1953a682aa83c22674813eaa
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/4787794
diff --git a/target/linux/mediatek/base-files/etc/sysupgrade.conf b/target/linux/mediatek/base-files/etc/sysupgrade.conf
new file mode 100644
index 0000000..530587f
--- /dev/null
+++ b/target/linux/mediatek/base-files/etc/sysupgrade.conf
@@ -0,0 +1,5 @@
+## This file should contains your platform's proprietary files
+## and directories that need to be preserved during OpenWRT sysupgrade.
+
+# /etc/example.conf
+/etc/wireless/