dw3000: rework stm locking strategy

Use wait_event_lock_irq to make the wait uninterrutpible. This needed
to use another lock than waitqueue's one.

Bug: 199454999
Change-Id: Id1b51ead3b8fb9d72899699f8c35136d7cbf34c7
Signed-off-by: Jean-Michel RIOT <jean-michel.riot@qorvo.com>