Add the description of CLI commands to the generated index.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

On the sandbox called without "--terminal raw" CTRL+C leaves U-Boot,
"ESC/CTRL+C to quit" is misleading.

Let's remove CTRL+C to quit key handling from bootmenu and eficonfig menu.

Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

The bootmenu enumerates the UEFI boot options
for boot device selection.
This commit adds the description how the UEFI boot work
in bootmenu. This commit also adds "Synopsis", "Description"
and "Configuration" sections to follow the U-Boot command
documentation format.

Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

%s/cammand/command/
%s/sequencies/sequences/

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

Signed-off-by: Tom Rini <trini@konsulko.com>

Currently all shell command docs are put in the doc/usage root.
Let's group them into cmd/ sub-directory.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>