driver-core, libnvdimm: Let device subsystems add local lockdep coverage

For good reason, the standard device_lock() is marked
lockdep_set_novalidate_class() because there is simply no sane way to
describe the myriad ways the device_lock() ordered with other locks.
However, that leaves subsystems that know their own local device_lock()
ordering rules to find lock ordering mistakes manually. Instead,
introduce an optional / additional lockdep-enabled lock that a subsystem
can acquire in all the same paths that the device_lock() is acquired.

A conversion of the NFIT driver and NVDIMM subsystem to a
lockdep-validate device_lock() scheme is included. The
debug_nvdimm_lock() implementation implements the correct lock-class and
stacking order for the libnvdimm device topology hierarchy.

Yes, this is a hack, but hopefully it is a useful hack for other
subsystems device_lock() debug sessions. Quoting Greg:

    "Yeah, it feels a bit hacky but it's really up to a subsystem to mess up
     using it as much as anything else, so user beware :)

     I don't object to it if it makes things easier for you to debug."

Cc: Ingo Molnar <[email protected]>
Cc: Ira Weiny <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Dave Jiang <[email protected]>
Cc: Keith Busch <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Vishal Verma <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Signed-off-by: Dan Williams <[email protected]>
Acked-by: Greg Kroah-Hartman <[email protected]>
Reviewed-by: Ira Weiny <[email protected]>
Link: https://lore.kernel.org/r/156341210661.292348.7014034644265455704.stgit@dwillia2-desk3.amr.corp.intel.com

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