[Bugfix] Fix MLA for GGUF

[SzymonOzog]

Now it should be correctly initialized although I'm seeing a bit of a performance degradation when using MLA (33 vs 37 tok/s)

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[cjackal]

It seems do the same fix as #14555

[mgoin]

LGTM. QQ Is there a way you could refactor this to use the shared _process_weights_after_loading function in this file?

[mgoin]

Closing in favor of #14555