ppc4xx: Remove redundant ft_board_setup() functions from some 4xx boards

This patch removes some ft_board_setup() functions from some 4xx boards.
This can be done since we now have a default weak implementation for this
in cpu/ppc4xx/fdt.c. Only board in need for a different/custom
implementation like canyonlands need their own version.

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