feat(linux): Add Post Quantum Cryptography documentation

[ti-kamlesh]

Add PQC documentation page covering NIST-standardized algorithms (ML-KEM, ML-DSA, SLH-DSA) supported via OpenSSL 3.5.x out of the box.

Enable the page for all devices with OpenSSL 3.5.x support:

• AM62AX, AM62DX, AM62LX, AM62PX, AM62X
• AM64X
• J721E, J721S2, J722S, J7200, J742S2, J784S4

[ti-kamlesh]

@StaticRocket on vale checks, acronym expansion is per paragraph. If i expand per paragraph it becomes hard to read.

"The RedHat.Definitions rule resets per paragraph — it doesn't remember a definition from one paragraph to the
next. So no matter where I write "Key Encapsulation Mechanism (KEM)", it will flag "KEM" again in every other paragraph. This means inline expansions
alone can't fix this.

There are three real options:

1. Add to accept.txt (minimal: KEM, DSA, SLH, GCM, SHAKE) — cleanest fix
2. Disable the rule in .vale.ini with RedHat.Definitions = NO
3. Wrap the whole doc with .. vale off / .. vale on RST comments"

Let me know your suggestion

[StaticRocket]

@ti-kamlesh

The RedHat.Definitions rule resets per paragraph

That's not right. Where did you get that information?

The reason you are getting warnings is because compound acronyms need both parts explained separately. That, and the explanation must precede the first use. The following is the correct way to do this:

Module Lattice (ML) Digital Signature Algorithm (DSA) or ML-DSA, based on CRYSTALS-Dilithium

[github-actions]

New warnings found with rstcheck:

source/linux/Foundational_Components/System_Security/Post_Quantum_Cryptography.rst:31: (WARNING/2) Title overline too short.
source/linux/Foundational_Components/System_Security/Post_Quantum_Cryptography.rst:31: (WARNING/2) Title overline too short.
source/linux/Foundational_Components/System_Security/Post_Quantum_Cryptography.rst:182: (WARNING/2) Title overline too short.
source/linux/Foundational_Components/System_Security/Post_Quantum_Cryptography.rst:182: (WARNING/2) Title overline too short.

[VeeruPrudhvi]

LGTM