hg: jdk/jdk: 8236595: Add more comments about how to setup simulated NVRAM before run java/nio/MappedByteBuffer/PmemTest.java

[xu.y.yin at oracle.com]

Changeset: 3782f2958116
Author:    xyin
Date:      2020-01-06 11:29 +0800
URL:       https://hg.openjdk.java.net/jdk/jdk/rev/3782f2958116

8236595: Add more comments about how to setup simulated NVRAM before run java/nio/MappedByteBuffer/PmemTest.java
Reviewed-by: alanb, adinn

! test/jdk/java/nio/MappedByteBuffer/PmemTest.java