ACPI: NFIT: Fix unlock on error in scrub_show()

We change the locking in this function and forgot to update this error
path so we are accidentally still holding the "dev->lockdep_mutex".

Fixes: 87a30e1f ("driver-core, libnvdimm: Let device subsystems add local lockdep coverage")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Acked-by: Dan Williams <dan.j.williams@intel.com>
Cc: 5.3+ <stable@vger.kernel.org> # 5.3+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>