bswap.h: Include <endian.h> on Haiku for bswap operations

bswap.h: Include <endian.h> on Haiku for bswap operations

Haiku puts the bswap* functions in <endian.h>; pull in that
include file on that platform.

Signed-off-by: David Carlier <devnexen@gmail.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20200703145614.16684-7-peter.maydell@linaro.org
[PMM: Expanded commit message]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>