board: Move show_board_info() comment to header file

Move this comment to its prototype and tidy it up a bit.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/include/init.h b/include/init.h
index d57a24f..9a1951d 100644
--- a/include/init.h
+++ b/include/init.h
@@ -292,6 +292,17 @@
 
 /* common/board_info.c */
 int checkboard(void);
+
+/**
+ * show_board_info() - Show board information
+ *
+ * Check sysinfo for board information. Failing that if the root node of the DTB
+ * has a "model" property, show it.
+ *
+ * Then call checkboard().
+ *
+ * Return 0 if OK, -ve on error
+ */
 int show_board_info(void);
 
 /**