RFR(S): 8241911: AArch64: Fix a potential register clash issue in reduce_add2I

[Yang Zhang]

Hi,

Could you please help to review this patch?

In original reduce_add2I, dst may be the same as tmp2, which may get incorrect result.
Some reduction operation instruct code formats are also cleaned up.

JBS: https://bugs.openjdk.java.net/browse/JDK-8241911
Webrev: http://cr.openjdk.java.net/~yzhang/8241911/webrev.00/


Regards
Yang