wifi: mt76: mt7925: pass mlink to set_link_key()

wifi: mt76: mt7925: pass mlink to set_link_key()

Drop the mt792x_sta_to_link() lookup in mt7925_set_link_key() and pass
the resolved mlink from the caller instead. The link context is already
known at the call site, making the lookup redundant.

This keeps the helper lookup-free and makes link ownership explicit.

No functional change intended.

Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Link: https://patch.msgid.link/20260306232238.2039675-11-sean.wang@kernel.org
Signed-off-by: Felix Fietkau <nbd@nbd.name>