RFR: 8230841: Remove oopDesc::equals()

[Per Liden]

With the removal of Access::equals() in JDK-8230808, there's no longer 
any need to treat oop equality in a special way. Therefore, we can 
remove oopDesc::equals() and oopDesc::equals_raw().

Bug: https://bugs.openjdk.java.net/browse/JDK-8230841
Webrev: http://cr.openjdk.java.net/~pliden/8230841/webrev.0

Testing: Currently running through tier1-3 in all platforms

/Per