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>
diff --git a/include/configs/M5253DEMO.h b/include/configs/M5253DEMO.h
index 7421b57..5d97874 100644
--- a/include/configs/M5253DEMO.h
+++ b/include/configs/M5253DEMO.h
@@ -32,6 +32,10 @@
 #	define CONFIG_ENV_IS_IN_FLASH	1
 #endif
 
+#define LDS_BOARD_TEXT \
+        . = DEFINED(env_offset) ? env_offset : .; \
+        common/env_embedded.o (.text*);
+
 /*
  * Command line configuration.
  */