[APX CCMP] Adjust startegy for selecting ccmp candidates

[APX CCMP] Adjust startegy for selecting ccmp candidates

For general ccmp scenario, the tree sequence is like

_1 = (a < b)
_2 = (c < d)
_3 = _1 & _2

current ccmp expanding will try to swap compare order for _1 and _2,
compare the expansion cost/cost2 for expanding _1 or _2 first, then
return the sequence with lower cost.

It is possible that one expansion succeeds and the other fails.
For example, x86 has int ccmp but not fp ccmp, so a combined fp and
int comparison must be ordered such that the fp comparison happens
first.  The costs are not meaningful for failed expansions.

Check the expand_ccmp_next result ret and ret2, returns the valid one
before cost comparison.

gcc/ChangeLog:

	* ccmp.cc (expand_ccmp_expr_1): Check ret and ret2 of
	expand_ccmp_next, returns the valid one first instead of
	comparing cost.