fpu/softfloat.c: Remove pointless shift of always-zero value

In float16_to_float32, when returning an infinity, just pass zero
as the mantissa argument to packFloat32(), rather than shifting
a value which we know must be zero.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

fpu/softfloat.c

@@ -3007,7 +3007,7 @@ float32 float16_to_float32(float16 a, flag ieee STATUS_PARAM)
         if (aSig) {
             return commonNaNToFloat32(float16ToCommonNaN(a STATUS_VAR) STATUS_VAR);
         }
-        return packFloat32(aSign, 0xff, aSig << 13);
+        return packFloat32(aSign, 0xff, 0);
     }
     if (aExp == 0) {
         int8 shiftCount;