Delete "boot=local", "noswap" unused values in kernel command line

Signed-off-by: Jaewon Jung <jw.jung@navercorp.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

Some Linux parameters can be set automatically by U-Boot, if it knows the
device being used. For example, since U-Boot knows the serial console
being used, it can add parameters for earlycon and console.

Add support for this.

Note that this is an experimental feature and we will see how useful it
turns out to be. It is very handy for ChromeOS, since otherwise it is very
difficult to manually determine the UART address or port number,
particularly in a script.

Provide an example of how this is used with ChromeOS.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

Add a bootflow command to update the command line more easily. This allows
changing a particular parameter rather than editing a very long strings.
It is also easier to handle with scripting.

The new 'bootflow cmdline' command allows getting and setting single
parameters.

Fix up the example output while we are here, since there are a few new
items.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

Some operating systems have a command line which can be adjusted before
booting. Store this in the bootflow so it can be controlled within
U-Boot.

Fix up the example output while we are here, since there are a few new
items.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

We use the terms 'distro' to mean extlinux but they are not really the
same. 'Distro' could refer to any method of booting a distribution,
whereas extlinux is a particular method.

Also we sometimes use syslinux, but it is better to use the same term in
all cases.

Rename distro to syslinux and also update bootstd uses of syslinux to use
extlinux instead.

Signed-off-by: Simon Glass <sjg@chromium.org>

Document the hunters and the new way that iteration works.

Signed-off-by: Simon Glass <sjg@chromium.org>

Add documentation for this feature, including the commands and full
devicetree bindings.

Signed-off-by: Simon Glass <sjg@chromium.org>