[][openwrt][mt7988][bsp][Add mt7988 subtarget into OpenWRT]

[Description]
Add mt7988 subtarget into OpenWRT

[Release-log]
N/A

Change-Id: Ia9bd92d04bf7f74875db01ac6f8f130ac418f33d
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/6653839
Build: srv_hbgsm110
diff --git a/openwrt_patches-21.02/001-add-mediatek-subtarget.patch b/openwrt_patches-21.02/001-add-mediatek-subtarget.patch
new file mode 100644
index 0000000..10b9802
--- /dev/null
+++ b/openwrt_patches-21.02/001-add-mediatek-subtarget.patch
@@ -0,0 +1,13 @@
+diff --git a/target/linux/mediatek/Makefile b/target/linux/mediatek/Makefile
+index c8ab5e0..01e993d 100644
+--- a/target/linux/mediatek/Makefile
++++ b/target/linux/mediatek/Makefile
+@@ -5,7 +5,7 @@ include $(TOPDIR)/rules.mk
+ ARCH:=arm
+ BOARD:=mediatek
+ BOARDNAME:=MediaTek Ralink ARM
+-SUBTARGETS:=mt7622 mt7623 mt7629
++SUBTARGETS:=mt7622 mt7623 mt7629 mt7986 mt7981 mt7988
+ FEATURES:=squashfs nand ramdisk fpu
+ 
+ KERNEL_PATCHVER:=5.4