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/sh7757lcr.h b/include/configs/sh7757lcr.h
index 4a5fd0d..2d6eb33 100644
--- a/include/configs/sh7757lcr.h
+++ b/include/configs/sh7757lcr.h
@@ -107,7 +107,7 @@
 #define SH7757LCR_ETHERNET_MAC_BASE	SH7757LCR_ETHERNET_MAC_BASE_SPI
 #define SH7757LCR_ETHERNET_MAC_SIZE	17
 #define SH7757LCR_ETHERNET_NUM_CH	2
-#define BOARD_LATE_INIT			1
+#define CONFIG_BOARD_LATE_INIT
 
 /* Gigabit Ether */
 #define SH7757LCR_GIGA_ETHERNET_NUM_CH	2