fs: ext4: implement opendir, readdir, closedir

For accessing directories from the EFI sub-system a file system must
implement opendir, readdir, closedir. Provide the missing implementation.

With this patch the eficonfig command can be used to define load options
for the ext4 file system.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
3 files changed