RFR: JDK-8209801: Remove C1_WRITE_ACCESS and C1_READ_ACCESS decorators

[Roman Kennke]

This is a cleanup. Back when this code has been introduced I asked for
those additional decorators, since then we introduced more generic
non-C1 decorators with the same semantics. Let's use them everywhere.

It's only used in modRefBarrierSetC1.cpp, and contrary to what I was
originally thinking, we don't need it in Shenandoah either. So maybe, if
we figure out another way to handle ModRefBarrierSetC1, we could just as
well remove them altogether. I don't mind keeping them though.

Bug:
https://bugs.openjdk.java.net/browse/JDK-8209801
Webrev:
http://cr.openjdk.java.net/~rkennke/JDK-8209801/webrev.00/

Testing: hotspot/tier1


Ok? Also, counts as trivial?


Roman