"hw/arm/boot.h" is only required on the source file.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Luc Michel <luc.michel@amd.com>
Message-id: 20231025065316.56817-6-philmd@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>