ipc: get rid of ipc_lock_down()

ipc: get rid of ipc_lock_down()

Remove the ipc_lock_down() routines: they used to call idr_find() locklessly
(given that the ipc ids lock was already held), so they are not needed
anymore.

Signed-off-by: Nadia Derbey <[email protected]>
Acked-by: "Paul E. McKenney" <[email protected]>
Cc: Manfred Spraul <[email protected]>
Cc: Jim Houston <[email protected]>
Cc: Pierre Peiffer <[email protected]>
Acked-by: Rik van Riel <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>