Add Kconfig options SPL_ENV_* and TPL_ENV_* and simplify Makefile.
This allows SPL/TPL image has different environment setting from
full feature U-Boot.

Signed-off-by: York Sun <york.sun@nxp.com>

When U-Boot started using SPDX tags we were among the early adopters and
there weren't a lot of other examples to borrow from.  So we picked the
area of the file that usually had a full license text and replaced it
with an appropriate SPDX-License-Identifier: entry.  Since then, the
Linux Kernel has adopted SPDX tags and they place it as the very first
line in a file (except where shebangs are used, then it's second line)
and with slightly different comment styles than us.

In part due to community overlap, in part due to better tag visibility
and in part for other minor reasons, switch over to that style.

This commit changes all instances where we have a single declared
license in the tag as both the before and after are identical in tag
contents.  There's also a few places where I found we did not have a tag
and have introduced one.

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

Last user of this option went away in commit:

fdc7718999 ("board: usb_a9263: Update to support DT and DM")

Signed-off-by: Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>

We plan to move to a environment access via drivers for each location
where the environment can be stored. Add an implementation for this. So
far it is not used, but will be pressed into service in a future patch.

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

About a quarter of the files in common/ relate to the environment. It
seems better to put these into their own subdirectory and remove the
prefix.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>