cosmetic: s/BOARD_LATE_INIT/CONFIG_BOARD_LATE_INIT

This renames BOARD_LATE_INIT to CONFIG_BOARD_LATE_INIT.
Along the way it removes some leftover

 #define BOARD_LATE_INIT		1

and adds some basic documentation for board specific
callbacks in README.

Signed-off-by: Helmut Raiger <helmut.raiger@hale.at>
Acked-by: Stefano Babic <sbabic@denx.de>
diff --git a/include/configs/nhk8815.h b/include/configs/nhk8815.h
index 13d1e66..20db397 100644
--- a/include/configs/nhk8815.h
+++ b/include/configs/nhk8815.h
@@ -96,7 +96,7 @@
 #define CONFIG_SYS_MEMTEST_END		0x0FFFFFFF
 #define CONFIG_SYS_MALLOC_LEN		(CONFIG_ENV_SIZE + 256 * 1024)
 
-#define BOARD_LATE_INIT		/* call board_late_init during start up */
+#define CONFIG_BOARD_LATE_INIT	/* call board_late_init during start up */
 
 /* timing informazion */
 #define CONFIG_SYS_HZ		1000 /* Mandatory... */