device-core: Kill the lockdep_mutex

Per Peter [1], the lockdep API has native support for all the use cases
lockdep_mutex was attempting to enable. Now that all lockdep_mutex users
have been converted to those APIs, drop this lock.

Link: https://lore.kernel.org/r/Ylf0dewci8myLvoW@hirez.programming.kicks-ass.net

 [1]
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/165055522548.3745911.14298368286915484086.stgit@dwillia2-desk3.amr.corp.intel.com


Signed-off-by: Dan Williams <dan.j.williams@intel.com>