[AArch64] Change the cost of fma and fmuladd to match fmul. (#152963) As fmul and fmadd are so similar, their performance characteristics tend to be the same on most platforms, at least in terms of reciprocal throughputs. Processors capable of performing a given number of fmul per cycle can usually perform the same number of fma, with the extra add being relatively simple on top. This patch makes the scores of the two operations the same, which brings the throughput cost of a fma/fmuladd to 2, and the latency to 3, which are the defaults for fmul. Note that we might also want to change the throughput cost of a fmul to 1, as most processors have ample bandwidth for them, but they should still stay in-line with one another.
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