softfloat: Reinstate accidentally disabled target-specific NaN handling

Include config.h in softfloat.c, so that the target specific ifdefs in
softfloat-specialize.h are evaluated correctly. This was accidentally
broken in commit 789ec7ce when config-target.h was removed from
softfloat.h, and means that most targets will have been returning the
wrong results for calculations involving NaNs.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NBlue Swirl <blauwirbel@gmail.com>

fpu/softfloat.c

@@ -35,6 +35,11 @@ these four paragraphs for those parts of this code that are retained.
 
 =============================================================================*/
 
+/* softfloat (and in particular the code in softfloat-specialize.h) is
+ * target-dependent and needs the TARGET_* macros.
+ */
+#include "config.h"
+
 #include "softfloat.h"
 
 /*----------------------------------------------------------------------------