cli: Add a command to show cmdline history

There is a function for this but it is never used. Showing the history is
a useful feature, so add a new 'history' command.

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

doc/usage/cmd/history.rst

@@ -0,0 +1,67 @@
+.. SPDX-License-Identifier: GPL-2.0+:
+
+history command
+===============
+
+Synopis
+-------
+
+::
+
+    history
+
+Description
+-----------
+
+The *history* command shows a list of previously entered commands on the
+command line. When U-Boot starts, this it is initially empty. Each new command
+entered is added to the list.
+
+Normally these commands can be accessed by pressing the `up arrow` and
+`down arrow` keys, which cycle through the list. The `history` command provides
+a simple way to view the list.
+
+Example
+-------
+
+This example shows entering three commands, then `history`. Note that `history`
+itself is added to the list.
+
+::
+
+    => bootflow scan -l
+    Scanning for bootflows in all bootdevs
+    Seq  Method       State   Uclass    Part  Name                      Filename
+    ---  -----------  ------  --------  ----  ------------------------  ----------------
+    Scanning global bootmeth 'firmware0':
+    Hunting with: simple_bus
+    Found 2 extension board(s).
+    Scanning bootdev 'mmc2.bootdev':
+    Scanning bootdev 'mmc1.bootdev':
+      0  extlinux     ready   mmc          1  mmc1.bootdev.part_1       /extlinux/extlinux.conf
+    No more bootdevs
+    ---  -----------  ------  --------  ----  ------------------------  ----------------
+    (1 bootflow, 1 valid)
+    => bootflow select 0
+    => bootflow info
+    Name:      mmc1.bootdev.part_1
+    Device:    mmc1.bootdev
+    Block dev: mmc1.blk
+    Method:    extlinux
+    State:     ready
+    Partition: 1
+    Subdir:    (none)
+    Filename:  /extlinux/extlinux.conf
+    Buffer:    aebdea0
+    Size:      253 (595 bytes)
+    OS:        Fedora-Workstation-armhfp-31-1.9 (5.3.7-301.fc31.armv7hl)
+    Cmdline:   (none)
+    Logo:      (none)
+    FDT:       <NULL>
+    Error:     0
+    => history
+    bootflow scan -l
+    bootflow select 0
+    bootflow info
+    history
+    =>