ppc4xx: Fix Canyonlands and Glacier default environment for fdt usage

ppc4xx: Fix Canyonlands and Glacier default environment for fdt usage

This patch fixes the Canyonlands and Glacier default environment to better
fit to the arch/powerpc device-tree kernels. The variables dealing with
arch/ppc booting are removed, since these boards are supported only in
arch/powerpc. Glacier uses the same config file as Canyonlands.

Also, the Glacier now uses non-FPU rootpath, since 460GT has no FPU.

Signed-off-by: Stefan Roese <sr@denx.de>