softfloat: make float_muladd_negate_* flags independent

Flags passed into float{32,64}_muladd are treated as bits; assign
independent bits to float_muladd_negate_* to allow precise control over
what gets negated in float{32,64}_muladd.
Signed-off-by: NMax Filippov <jcmvbkbc@gmail.com>
Reviewed-by: NAurelien Jarno <aurelien@aurel32.net>
Signed-off-by: NBlue Swirl <blauwirbel@gmail.com>

fpu/softfloat.h

@@ -219,7 +219,7 @@ void float_raise( int8 flags STATUS_PARAM);
 enum {
     float_muladd_negate_c = 1,
     float_muladd_negate_product = 2,
-    float_muladd_negate_result = 3,
+    float_muladd_negate_result = 4,
 };
 
 /*----------------------------------------------------------------------------