Kconfig: Sort the memory commands

These are currently not quite in alphabetical order. Before adding more,
sort them. Not all options have a CMD_ prefix, so ignore that when
sorting.

Signed-off-by: Simon Glass <sjg@chromium.org>
Suggested-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>