[aarch64-port-dev ] RFR: 8186671: Use `yield` instruction in SpinPause on linux-aarch64

[Dmitry Chuyko]

Please review a change in SpinPause implementation.

related study: 
http://cr.openjdk.java.net/~dchuyko/8186670/yield/spinwait.html
rfe: https://bugs.openjdk.java.net/browse/JDK-8186671
webrev: http://cr.openjdk.java.net/~dchuyko/8186671/webrev.00/

The function was moved to platform .S file and now contains yield 
instruction.

--
Dmitry Chuyko