cmd: rework "license" command

The previous commit ("add a new command to show .config contents")
improves the basic infrastructure of "embed a compressed file into
the U-Boot image, and print it by a command". The same pattern for
the "license" command.

This commit reworks the command to improve the following:

[1] Improve log style

Kbuild style log

GZIP cmd/license_data.gz
CHK cmd/license_data_gz.h
UPD cmd/license_data_gz.h
CHK cmd/license_data_size.h
UPD cmd/license_data_size.h

instead of the bare Make log:

cat ./Licenses/gpl-2.0.txt | gzip -9 -c | \
tools/bin2header license_gzip > ./include/license.h

[2] Collect related code into the "cmd" directory

Prior to this commit, the license.h was created by tools/Makefile,
placed under the "include" directory, included from cmd/license.c,
and deleted by the top-level Makefile. It is not a good idea to
scatter related code.

[3] Drop the fixed-malloc size LICENSE_MAX

Just allocate the minimum required size of buffer because we know
the size of the original gpl-2.0.txt.

[4] Fix more issues

Terminate the buffer with zero to prevent puts() from over-running.
Add "static" to do_license.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

cmd: add a new command "config" to show .config contents

This feature is inspired by /proc/config.gz of Linux. In Linux,
if CONFIG_IKCONFIG is enabled, the ".config" file contents are
embedded in the kernel image. If CONFIG_IKCONFIG_PROC is also
enabled, the ".config" contents are exposed to /proc/config.gz.
Users can do "zcat /proc/config.gz" to check which config options
are enabled on the running kernel image.

The idea is almost the same here; if CONFIG_CMD_CONFIG is enabled,
the ".config" contents are compressed and saved in the U-Boot image,
then printed by the new command "config".

The usage is quite simple. Enable CONFIG_CMD_CONFIG, then run
> config
from the command line interface. The ".config" contents will be
printed on the console.

This feature increases the U-Boot image size by about 4KB (this is
mostly due to the gzip-compressed .config file). By default, it is
enabled only for Sandbox because we do not care about the memory
footprint on it. Of course, this feature is architecture agnostic,
so you can enable it on any board if the image size increase is
acceptable for you.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Simon Glass <sjg@chromium.org>