api: Rename legacy API files and examples

The API is not very useful these days, since it doesn't support driver
model. It is laborious to add new functions to the API as there are so
many needed.

A better approach would be to create a library containing all of U-Boot,
then have the API be generated by a script containing a list of
functions, perhaps with wildcards. Then a stub could be created, with
a list of entry points, which links with and calls through into the
library.

In preparation for heading in this direction, rename some of the
existing files and directories:

- examples/api -> examples/legacy_api
- include/api*.h -> include/legacy_api*.h
- API_BUILD to LEGACY_API_BUILD

Co-developed-by: Claude <noreply@anthropic.com>

examples/legacy_api/Makefile

@@ -2,8 +2,8 @@
 #
 # (C) Copyright 2007 Semihalf
 
-# Provide symbol API_BUILD to signal that the API example is being built.
-KBUILD_CPPFLAGS += -DAPI_BUILD
+# Provide symbol LEGACY_API_BUILD to signal that the legacy API example is being built.
+KBUILD_CPPFLAGS += -DLEGACY_API_BUILD
 
 ifeq ($(ARCH),powerpc)
 LOAD_ADDR = 0x40000
@@ -26,13 +26,13 @@ endif
 # Resulting ELF and binary exectuables will be named demo and demo.bin
 extra-y = demo
 
-# Source files located in the examples/api directory
+# Source files located in the examples/legacy_api directory
 OBJ-y += crt0.o
 OBJ-y += demo.o
 OBJ-y += glue.o
 OBJ-y += libgenwrap.o
 
-# Source files which exist outside the examples/api directory
+# Source files which exist outside the examples/legacy_api directory
 EXT_COBJ-y += lib/crc32.o
 EXT_COBJ-y += lib/ctype.o
 EXT_COBJ-y += lib/div64.o

examples/legacy_api/demo.c

@@ -8,7 +8,7 @@
 #include <stdio.h>
 #include <env.h>
 #include <linux/types.h>
-#include <api_public.h>
+#include <legacy_api_public.h>
 
 #include "glue.h"
 

examples/legacy_api/glue.c

@@ -5,7 +5,7 @@
 
 #include <env.h>
 #include <linux/types.h>
-#include <api_public.h>
+#include <legacy_api_public.h>
 #include <u-boot/crc.h>
 
 #include "glue.h"

examples/legacy_api/libgenwrap.c

@@ -13,7 +13,7 @@
 #include <hang.h>
 #include <linux/delay.h>
 #include <linux/types.h>
-#include <api_public.h>
+#include <legacy_api_public.h>
 
 #include "glue.h"