sandbox: Avoid using malloc() for system state

This state is not accessible to the running U-Boot but at present it is
allocated in the emulated SDRAM. This doesn't seem very useful. Adjust
it to allocate from the OS instead.

The RAM buffer is currently not freed, but should be, so add that into
state_uninit(). Update the comment for os_free() to indicate that NULL is
a valid parameter value.

Note that the strdup() in spl_board_load_image() is changed as well, since
strdup() allocates memory in the RAM buffer.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/sandbox/cpu/os.c b/arch/sandbox/cpu/os.c
index d23aad3..f5000e6 100644
--- a/arch/sandbox/cpu/os.c
+++ b/arch/sandbox/cpu/os.c
@@ -153,7 +153,7 @@
 		printf("Cannot seek to start of file '%s'\n", fname);
 		goto err;
 	}
-	*bufp = malloc(size);
+	*bufp = os_malloc(size);
 	if (!*bufp) {
 		printf("Not enough memory to read file '%s'\n", fname);
 		ret = -ENOMEM;
@@ -391,8 +391,8 @@
 	state->argv = argv;
 
 	/* dynamically construct the arguments to the system getopt_long */
-	short_opts = malloc(sizeof(*short_opts) * num_options * 2 + 1);
-	long_opts = malloc(sizeof(*long_opts) * (num_options + 1));
+	short_opts = os_malloc(sizeof(*short_opts) * num_options * 2 + 1);
+	long_opts = os_malloc(sizeof(*long_opts) * (num_options + 1));
 	if (!short_opts || !long_opts)
 		return 1;
 
@@ -471,7 +471,7 @@
 
 	while (node) {
 		next = node->next;
-		free(node);
+		os_free(node);
 		node = next;
 	}
 }
@@ -496,7 +496,7 @@
 	/* Create a buffer upfront, with typically sufficient size */
 	dirlen = strlen(dirname) + 2;
 	len = dirlen + 256;
-	fname = malloc(len);
+	fname = os_malloc(len);
 	if (!fname) {
 		ret = -ENOMEM;
 		goto done;
@@ -509,7 +509,7 @@
 			ret = errno;
 			break;
 		}
-		next = malloc(sizeof(*node) + strlen(entry->d_name) + 1);
+		next = os_malloc(sizeof(*node) + strlen(entry->d_name) + 1);
 		if (!next) {
 			os_dirent_free(head);
 			ret = -ENOMEM;
@@ -518,10 +518,10 @@
 		if (dirlen + strlen(entry->d_name) > len) {
 			len = dirlen + strlen(entry->d_name);
 			old_fname = fname;
-			fname = realloc(fname, len);
+			fname = os_realloc(fname, len);
 			if (!fname) {
-				free(old_fname);
-				free(next);
+				os_free(old_fname);
+				os_free(next);
 				os_dirent_free(head);
 				ret = -ENOMEM;
 				goto done;
@@ -555,7 +555,7 @@
 
 done:
 	closedir(dir);
-	free(fname);
+	os_free(fname);
 	return ret;
 }
 
@@ -672,7 +672,7 @@
 	for (argc = 0; (*argvp)[argc]; argc++)
 		;
 
-	argv = malloc((argc + count + 1) * sizeof(char *));
+	argv = os_malloc((argc + count + 1) * sizeof(char *));
 	if (!argv) {
 		printf("Out of memory for %d argv\n", count);
 		return -ENOMEM;
@@ -755,7 +755,7 @@
 		os_exit(2);
 
 	err = execv(fname, argv);
-	free(argv);
+	os_free(argv);
 	if (err) {
 		perror("Unable to run image");
 		printf("Image filename '%s'\n", fname);