Move board.c to the dfe board directory.

Move default environment to established #defines -- remove setenv() calls.

diff --git a/cpu/arm_cortexa8/pele/board.c b/board/xilinx/dfe/board.c
similarity index 100%
rename from cpu/arm_cortexa8/pele/board.c
rename to board/xilinx/dfe/board.c