RFR: 8289138: G1: Remove redundant is-marking-active checks in C1 barrier

[Thomas Schatzl]

On Fri, 24 Jun 2022 12:00:44 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Simple change of removing a redundant check in C1 barrier code.
> 
> Test: tier1-3

Lgtm.

-------------

Marked as reviewed by tschatzl (Reviewer).

PR: https://git.openjdk.org/jdk/pull/9274