tests/fp/platform.h: include config-host.h

We get HOST_WORDS_BIGENDIAN from config-host.h, but the include
is missing. Fix it.

This fixes `make check-softfloat' on big endian hosts.
Reported-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NEmilio G. Cota <cota@braap.org>
Signed-off-by: NAlex Bennée <alex.bennee@linaro.org>

tests/fp/platform.h

@@ -29,6 +29,7 @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
+#include "config-host.h"
 
 #ifndef HOST_WORDS_BIGENDIAN
 #define LITTLEENDIAN 1