IPC Type-X: Prevent multiple writes to a C-buffer?

[todo]

Do I need to prevent multiple writes to the same buffer ID? In theory, I could use coff as a bitmap of used buffers, and prevent reuse this way, but I'm unsure of how the nintendo switch behaves here.

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https://github.com/roblabla42/KFS/blob/9a8c10d77d31d3449a2b790c386e9ae88b11ba62/kernel/src/ipc/session.rs#L539-L549

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This issue was generated by todo based on a TODO comment in 9a8c10d when #229 was merged. cc @roblabla.