RFR: 8261650: Add a comment with details for MTLVC_MAX_INDEX

[Jayathirth D V]

On Mon, 9 May 2022 07:02:51 GMT, Ajit Ghaisas <aghaisas at openjdk.org> wrote:

> This is a trivial fix which adds more details about the constant MTLVC_MAX_INDEX.
> This had come up during the review of [JDK-8261632](https://bugs.openjdk.java.net/browse/JDK-8261632).

Marked as reviewed by jdv (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/8592