um: vector: remove vp->lock

This lock is useless, all the places that are using
it for some locking will already hold the RTNL. Just
remove it.

Link: https://patch.msgid.link/20240703184606.19aa35b14959.I9cf5f2c4e35abd06cc89bf2e990fa755eb8e5f0f@changeid


Acked-By: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>