RFR: 8149019: remove redundant modifiers

[Doug Simon]

JVMCI code is checked by Checkstyle and recent Checkstyle releases have introduced better detection of redundant modifiers. To ensure JVMCI continues to benefit from automated code style checking, it makes sense to keep up with Checkstyle and address style issues detected by newer versions.

https://bugs.openjdk.java.net/browse/JDK-8149019
http://cr.openjdk.java.net/~dnsimon/8149019

-Doug