RFR: 8342860: Fix more NULL usage backsliding

[Sonia Zaldana Calles]

On Fri, 1 Nov 2024 13:35:56 GMT, theoweidmannoracle <duke at openjdk.org> wrote:

> - Changed several "NULL" in comments to "null"
> - Changed several `NULL` in code to `nullptr`

I am not a Reviewer but I left a small comment. 

Cheers!

src/hotspot/os/linux/cgroupSubsystem_linux.cpp line 1:

> 1: /*

Missing copyright update.

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Changes requested by szaldana (Committer).

PR Review: https://git.openjdk.org/jdk/pull/21826#pullrequestreview-2413904415
PR Review Comment: https://git.openjdk.org/jdk/pull/21826#discussion_r1828249544