fs: fat: add rename

The implementation roughly follows the POSIX specification for
rename() [1]. The ordering of operations attempting to minimize the chance
for data loss in unexpected circumstances.

The 'mv' command was implemented as a front end for the rename operation
as that is what most users are likely familiar with in terms of behavior.

The 'FAT_RENAME' Kconfig option was added to prevent code size increase on
size-oriented builds like SPL.

[1] https://pubs.opengroup.org/onlinepubs/9799919799/functions/rename.html

Signed-off-by: Gabriel Dalimonte <gabriel.dalimonte@gmail.com>

cmd/fs.c

@@ -110,3 +110,17 @@ U_BOOT_CMD(
 	fstypes, 1, 1, do_fstypes_wrapper,
 	"List supported filesystem types", ""
 );
+
+static int do_mv_wrapper(struct cmd_tbl *cmdtp, int flag, int argc,
+			 char *const argv[])
+{
+	return do_mv(cmdtp, flag, argc, argv, FS_TYPE_ANY);
+}
+
+U_BOOT_CMD(
+	mv,	5,	1,	do_mv_wrapper,
+	"rename/move a file/directory",
+	"<interface> [<dev[:part]>] <old_path> <new_path>\n"
+	"    - renames/moves a file/directory in 'dev' on 'interface' from\n"
+	"      'old_path' to 'new_path'"
+);