[source] mvebu: fix sysupgrade

[LEDE Commits]

blogic pushed a commit to source.git, branch master:
https://git.lede-project.org/15cb19f02a8c7fdcdb87b068cf098a2c03e39fce

commit 15cb19f02a8c7fdcdb87b068cf098a2c03e39fce
Author: Aaron Curley <accwebs at gmail.com>
AuthorDate: Sun Oct 2 13:15:25 2016 -0700

    mvebu: fix sysupgrade
    
    sysupgrade command fails due to missing U-Boot environment-processing binaries on sysupgrade ramdisk. The missing binaries result in the following output:
    	Switching to ramdisk...
    	Performing system upgrade...
    	ash: /usr/sbin/fw_printenv: not found
    	ash: fw_setenv: not found
    	ash: touch: not found
    	cannot find target partition
    
    Fixes FS#197.
    
    Signed-off-by: Aaron Curley <accwebs at gmail.com>
---
 target/linux/mvebu/base-files/lib/upgrade/linksys.sh | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/target/linux/mvebu/base-files/lib/upgrade/linksys.sh b/target/linux/mvebu/base-files/lib/upgrade/linksys.sh
index baa29dc..d12c32b 100644
--- a/target/linux/mvebu/base-files/lib/upgrade/linksys.sh
+++ b/target/linux/mvebu/base-files/lib/upgrade/linksys.sh
@@ -89,3 +89,5 @@ linksys_preupgrade() {
 	esac
 }
 
+append sysupgrade_pre_upgrade linksys_preupgrade
+