[openwrt/openwrt] mediatek: add missing SPDX header

[LEDE Commits]

rmilecki pushed a commit to openwrt/openwrt.git, branch openwrt-23.05:
https://git.openwrt.org/feb5b072efe1e9777e69039d1b4a0c6c238cb75f

commit feb5b072efe1e9777e69039d1b4a0c6c238cb75f
Author: David Bauer <mail at david-bauer.net>
AuthorDate: Sat Jul 22 17:40:56 2023 +0200

    mediatek: add missing SPDX header
    
    Signed-off-by: David Bauer <mail at david-bauer.net>
    (cherry picked from commit 36f7ececc21fe6698a75f5ce9fc3ebf6c96a1b97)
---
 target/linux/mediatek/dts/mt7981b-zyxel-nwa50ax-pro.dts | 1 +
 1 file changed, 1 insertion(+)

diff --git a/target/linux/mediatek/dts/mt7981b-zyxel-nwa50ax-pro.dts b/target/linux/mediatek/dts/mt7981b-zyxel-nwa50ax-pro.dts
index c6dc1e5c4e..d222cebb4f 100644
--- a/target/linux/mediatek/dts/mt7981b-zyxel-nwa50ax-pro.dts
+++ b/target/linux/mediatek/dts/mt7981b-zyxel-nwa50ax-pro.dts
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: (GPL-2.0-or-later OR MIT)
 /dts-v1/;
 
 #include "mt7981.dtsi"