match/forwprop: Simplify handling of cond_carry_add

So right there are two match patterns; one that handles
tree true edge is the addition and one where the false edge is
the addition.  But there is no reason why there can't be one
match pattern which handles both of them. The forwprop code
does not take care which edge is which. So let's merge them
into one match pattern called cond_carry_add.
This should have a small compile time (and memory usage due to
creating a tree in the match due to cond^ handling) improvement
as transversing the phi/cond only happens once.

Pushed as obvious after a Bootstrapped/test on x86_64-linux-gnu.

gcc/ChangeLog:

	* match.pd (cond_carry_add_neg): Rename to
	cond_carry_add.
	* tree-ssa-forwprop.cc (gimple_cond_carry_add_neg): Remove.
	(match_long_mul_phi): Don't call gimple_cond_carry_add_neg.

Signed-off-by: Andrea Pinski <andrew.pinski@oss.qualcomm.com>