RFR: 8342860: Fix more NULL usage backsliding

[theoweidmannoracle]

On Mon, 4 Nov 2024 19:10:50 GMT, Sonia Zaldana Calles <szaldana at openjdk.org> wrote:

>> - Changed several "NULL" in comments to "null"
>> - Changed several `NULL` in code to `nullptr`
>
> src/hotspot/os/linux/cgroupSubsystem_linux.cpp line 1:
> 
>> 1: /*
> 
> Missing copyright update.

Thanks for spotting this!

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PR Review Comment: https://git.openjdk.org/jdk/pull/21826#discussion_r1829109988