cpu9260: update board support

- update to new relocation code
- switch to boards.cfg
- get rid of LEGACY (still a little hack in .h to compile)
- add nand boot configuration
- boot tested for the following configurations :
	9260 (64MB RAM & nor boot)
	9260_nand (64MB RAM & nand boot)
	9G20_128M (128MB RAM & nor boot)
	9G20_nand_128M (128MB RAM & nand boot)
	(nor boot is using lowlevel init)

Signed-off-by: Eric Bénard <eric@eukrea.com>