[][OpenWrt Dev][Fix mmc upgrading script]

[Description]
Fix a condition checking error in mmc upgrading script

[Release-log]
N/A

Change-Id: I9b8d8dceebe3df287cd369c6d4ae7d72c839ae6e
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/6105790
1 file changed