gdbstub: fix-up copyright and license files

gdbstub: fix-up copyright and license files

When I started splitting gdbstub apart I was a little too boilerplate
with my file headers. Fix up to carry over Fabrice's copyright and the
LGPL license header.

Fixes: ae7467b1ac (gdbstub: move breakpoint logic to accel ops)
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20230302190846.2593720-3-alex.bennee@linaro.org>
Message-Id: <20230303025805.625589-3-richard.henderson@linaro.org>