Enable net console

[skbeh]

Enabling net console will simplify debugging, as connecting via TTL is not always easy.

I tried to enable it by adding the following changes and connect to the router with ./tools/netconsole 192.168.1.1, but there is always no reply.

diff --git a/uboot-mtk-20230718-09eda825/board/mediatek/mt7981/mt7981.env b/uboot-mtk-20230718-09eda825/board/mediatek/mt7981/mt7981.env
new file mode 100644
index 00000000..7daf03b8
--- /dev/null
+++ b/uboot-mtk-20230718-09eda825/board/mediatek/mt7981/mt7981.env
@@ -0,0 +1,3 @@
+stdout=nc
+stdin=nc
+ncip=192.168.1.2
diff --git a/uboot-mtk-20230718-09eda825/configs/mt7981_h3c_magic-nx30-pro_defconfig b/uboot-mtk-20230718-09eda825/configs/mt7981_h3c_magic-nx30-pro_defconfig
index 6d033e41..b9017a16 100644
--- a/uboot-mtk-20230718-09eda825/configs/mt7981_h3c_magic-nx30-pro_defconfig
+++ b/uboot-mtk-20230718-09eda825/configs/mt7981_h3c_magic-nx30-pro_defconfig
@@ -98,3 +98,5 @@ CONFIG_MTK_SPIM=y
CONFIG_TIMER=y
CONFIG_MTK_TIMER=y
CONFIG_HEXDUMP=y
+CONFIG_PROT_UDP=y
+CONFIG_NETCONSOLE=y