middle-end/116891 - fix (negate (IFN_FNMS@3 @0 @1 @2)) -> (IFN_FMA @0 @1 @2)

Transforming -fma (-a, b, -c) to fma (a, b, c) is only valid when
not rounding towards -inf or +inf as the sign of the multiplication
changes.

	PR middle-end/116891
	* match.pd ((negate (IFN_FNMS@3 @0 @1 @2)) -> (IFN_FMA @0 @1 @2)):
	Only enable for !HONOR_SIGN_DEPENDENT_ROUNDING.