[openwrt/openwrt] ath79: set lzma-loader variables to null by default

[LEDE Commits]

adrian pushed a commit to openwrt/openwrt.git, branch master:
https://git.openwrt.org/bf8c16dfa2cddd529f889510ca5fa5160606c325

commit bf8c16dfa2cddd529f889510ca5fa5160606c325
Author: Michael Pratt <mcpratt at pm.me>
AuthorDate: Sat May 8 17:34:30 2021 -0400

    ath79: set lzma-loader variables to null by default
    
    This fixes a small regression where the lzma-loader variable values
    are being shared between boards that require different configurations.
    
    If not set to "" globally, a device without these settings will just take
    the last values another device has set before in the queue.
    
    Fixes: 1b8bd17c2d07 ("ath79: lzma-loader: allow setting custom kernel magic")
    Signed-off-by: Michael Pratt <mcpratt at pm.me>
    [add detailed explanation to the commit message]
    Signed-off-by: Adrian Schmutzler <freifunk at adrianschmutzler.de>
---
 target/linux/ath79/image/Makefile | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/target/linux/ath79/image/Makefile b/target/linux/ath79/image/Makefile
index d8b8800d91..3c126f479e 100644
--- a/target/linux/ath79/image/Makefile
+++ b/target/linux/ath79/image/Makefile
@@ -70,6 +70,10 @@ define Device/Default
   BLOCKSIZE := 64k
   KERNEL := kernel-bin | append-dtb | lzma | uImage lzma
   KERNEL_INITRAMFS := kernel-bin | append-dtb | lzma | uImage lzma
+  LOADER_KERNEL_MAGIC :=
+  LOADER_FLASH_MAX :=
+  LOADER_FLASH_OFFS :=
+  LOADER_TYPE :=
   COMPILE :=
   IMAGES := sysupgrade.bin
   IMAGE/sysupgrade.bin = append-kernel | pad-to $$$$(BLOCKSIZE) | \