SPDX: Convert all of our single license tags to Linux Kernel style

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>

Add GPL-2.0+ SPDX-License-Identifier to source files

Signed-off-by: Wolfgang Denk <wd@denx.de>
[trini: Fixup common/cmd_io.c]
Signed-off-by: Tom Rini <trini@ti.com>

Fix references to the documentation files

Many boot image configuration files refer to the
appropriate documentation file, but these references
contain typos in the directory and file name. Fix
them. Also fix reference to doc/README.SPL file.

Signed-off-by: Anatolij Gustschin <agust@denx.de>
Cc: Prafulla Wadaskar <prafulla@marvell.com>
Cc: Stefano Babic <sbabic@denx.de>
Acked-by: Stefano Babic <sbabic@denx.de>

dreamplug: initial board support.

Copied wholeheartedly from board/Marvell/guruplug and modified to add support
for SPI NOR flash.

CONFIG_MACH_DREAMPLUG defined in include/configs/dreamplug.h until Linus's
kernel.org tree adds it to mach-types.h. Once it trickles down, the definition
can be removed from include/configs/dreamplug.h.

Signed-off-by: Jason Cooper <u-boot@lakedaemon.net>