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

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