[U-Boot] [U-Boot, v2, 42/42] README: Drop information about commands

[Philipp Tomsich]

> Most of this is duplicated in Kconfig help. Add some of that which is not,
> and remove the help from the README.
> 
> Signed-off-by: Simon Glass <sjg at chromium.org>
> Reviewed-by: Bin Meng <bmeng.cn at gmail.com>
> ---
> 
> Changes in v2:
> - Drop patch to convert CONFIG_CMD_MTDPARTS to Kconfig (already done)
> 
>  README               | 116 +--------------------------------------------------
>  cmd/Kconfig          |   4 +-
>  cmd/fastboot/Kconfig |   2 +
>  3 files changed, 6 insertions(+), 116 deletions(-)
> 

Reviewed-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>