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>

The debug environment which is stored in textfiles in the
scripts directory was reworked. Two usecase are now present
which can be executed simply from the default environment:
run develop: this configures the environment to setup the
             rootfs via nfs
run ramfs: this configures the environment to setup the
           rootfs in ram

Each architecture now has a "arch" variable which is used
to load the architecture specific debug scripts and to set
the rootpath for NFS.

Signed-off-by: Holger Brunck <holger.brunck@keymile.com>
Signed-off-by: Valentin Longchamp <valentin.longchamp@keymile.com>
cc: Heiko Schocher <hs@denx.de>
cc: Wolfgang Denk <wd@denx.de>

This is a first step to simplify the default environment. Move all
the environment variables which are only needed for debugging
purpose to textfiles in the scripts directory. In case of debugging
these files can be loaded via tftp into RAM and set via the env import
command. Other variables are identified as obsolete and were removed.

Signed-off-by: Holger Brunck <holger.brunck@keymile.com>
Signed-off-by: Valentin Longchamp <valentin.longchamp@keymile.com>
Acked-by: Heiko Schocher <hs@denx.de>
cc: Wolfgang Denk <wd@denx.de>
cc: Detlev Zundel <dzu@denx.de>