Only q35.c requires declarations from "hw/i386/pc.h", move it there.
Remove all the includes not used by "q35.h".

Acked-by: John Snow <jsnow@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20200228114649.12818-18-philmd@redhat.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>