uboot-imx

m68k: add architecture-specific u-boot.lds

Add architecture-specific u-boot.lds and remove all board-specific
u-boot.lds.

All the .text customization that was board-specific have been
moved inside the related include/configs, inside a
LDS_BOARD_TEXT define.

Signed-off-by: Angelo Dureghello <angelo@sysam.it>