nvdimm: Introduce guard() for nvdimm_bus_lock

Converting nvdimm_bus_lock/unlock to guard() to clean up usage
of gotos for error handling and avoid future mistakes of missed
unlock on error paths.

Link: https://lore.kernel.org/linux-cxl/20250917163623.00004a3c@huawei.com/


Suggested-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Acked-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>