km/common: add toolchain variable

Add a variable "toolchain" and configure the rootpath
for the nfsargs with this variable.

Signed-off-by: Holger Brunck <holger.brunck@keymile.com>
cc: Wolfgang Denk <wd@denx.de>

board/keymile/scripts/develop-common.txt

@@ -2,6 +2,7 @@ altbootcmd=run ${subbootcmds}
 bootcmd=run ${subbootcmds}
 configure=km_setboardid && saveenv && reset
 subbootcmds=tftpfdt tftpkernel nfsargs add_default boot
-nfsargs=setenv bootargs root=/dev/nfs rw nfsroot=${serverip}:/opt/eldk/${arch}
+nfsargs=setenv bootargs root=/dev/nfs rw nfsroot=${serverip}:${toolchain}/${arch}
 tftpkernel=tftpboot ${load_addr_r} ${hostname}/uImage
+toolchain=/opt/eldk
 rootfssize=0