RFR: Refactor asm acmp (aarch64)

[Roman Kennke]

Same as yesterday's refactoring in x86.

I chose 'cmpoops' as name for new assembly macro. cmp_oop_oop() doesn't
seem to fit the common naming pattern that well. Will rename the x86
side in followup patch too.

http://cr.openjdk.java.net/~rkennke/refactor_acmp_aarch64/webrev.00/
<http://cr.openjdk.java.net/%7Erkennke/refactor_acmp_aarch64/webrev.00/>

Roman