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>

microblaze: Fix stack usage in interrupt handler

Do not save registers below r1 stack pointer because
it is not checked by stack undeflow is not able to detect
it.

Signed-off-by: Michal Simek <michal.simek@xilinx.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>

microblaze: Fix msr handling in interrupt_handler

Fix ancient code which worked with MSR in a bad way.
Use rtid instruction which enable IRQs and jump.

Signed-off-by: Michal Simek <monstr@monstr.eu>

microblaze: Fix irq.S code

It is ancient code. There is possible to save several instructions
just if we use offset instead of addik

Signed-off-by: Michal Simek <monstr@monstr.eu>

microblaze: Move cpu/microblaze/* to arch/microblaze/cpu/*

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>