net: ethernet: mtk_wed: annotate RCU release in attach()

net: ethernet: mtk_wed: annotate RCU release in attach()

There are some sparse warnings in wifi, and it seems that
it's actually possible to annotate a function pointer with
__releases(), making the sparse warnings go away. In a way
that also serves as documentation that rcu_read_unlock()
must be called in the attach method, so add that annotation.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Link: https://patch.msgid.link/20250423150811.456205-2-johannes@sipsolutions.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>