ar71xx: Update merakinand.sh to fix sysupgrade

Remove reliance on /lib/upgrade/nand.sh as this is called by sysupgrade,
based on felix's comments at
https://lists.openwrt.org/pipermail/openwrt-devel/2015-December/037963.html



Signed-off-by: Chris R Blake <chrisrblake93@gmail.com>

SVN-Revision: 47889

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

@@ -7,7 +7,6 @@
 #
 . /lib/ar71xx.sh
 . /lib/functions.sh
-. /lib/upgrade/nand.sh
 
 get_magic_at() {
 	local mtddev=$1