Hi Sean,

[Zac Bowling]

This is a backport of the mutex protection fixes from the MT7925 driver to the
older MT7921 chipset. The MT7921 driver has the same mutex protection bugs
because MT7925 was forked from MT7921 and inherited these issues.

I don't have this chipset yet but I ordered it but someone else tested
this patch and solves a crash they had.

This patch addresses the same root cause as patches 2, 3, and 16 in my MT7925
patch series (v3 00/17) - missing mutex protection around interface iteration
when callbacks invoke MCU functions.

The key fix here is moving the mutex protection inside `mt7921_roc_abort_sync()`
rather than at call sites, to avoid nested mutex acquisition deadlocks in
suspend paths. This matches the corrected approach used in the MT7925 patches.

I hope you can find time to review the other 17 patches for the newer MT7925
chipset.

Thanks,
Zac