ar71xx: fix sysupgrade for Arduino Yun

Commit bb46b635df changed its partition scheme, but sysupgrade image
validation still uses the old format. This commit fixes it so that
force flag is not needed for sysupgrade.

Fixes: bb46b635df ("ar71xx: move Arduino Yun to generic building code")
Signed-off-by: Sungbo Eo <mans0n@gorani.run>
(cherry picked from commit 58dc1d0637425cfe023192466e6212009332b677)

target/linux/ar71xx/base-files/lib/upgrade/platform.sh

@@ -217,6 +217,7 @@ platform_check_image() {
 	archer-c60-v2|\
 	archer-c7-v4|\
 	archer-c7-v5|\
+	arduino-yun|\
 	bullet-m|\
 	bullet-m-xw|\
 	c-55|\
@@ -346,7 +347,6 @@ platform_check_image() {
 	ap152|\
 	ap91-5g|\
 	ap96|\
-	arduino-yun|\
 	bhr-4grv2|\
 	bxu2000n-2-a1|\
 	db120|\