RFR[tiny]: 8241482: AArch64: Fix a potential issue after JDK-8239549

[Pengfei Li]

Hi,

Could you help review this small fix of a potential issue in my previous
patch [1] for JDK-8239549?

JBS: https://bugs.openjdk.java.net/browse/JDK-8241482
Webrev: http://cr.openjdk.java.net/~pli/rfr/8241482/webrev.00/

This adds one more effect of "TEMP_DEF dst" in the AArch64 matching rule
for MulAddVS2VI node to avoid the conflict between register dst and tmp.
The existing effect "TEMP tmp" just guarantees register tmp is different
from any of the input registers, but cannot guarantee tmp is different
from the dst register. As dst is also used as another temp register in
the code, the result would be wrong if tmp and dst happen to be the same
one.

We should take extra care of register conflict when using NEON temps in
the future.

[TESTS] Tier1 passed.

[1] https://hg.openjdk.java.net/jdk/jdk/rev/ff1f4b5e0c9a

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Thanks,
Pengfei