nvdimm/pfn_dev: Avoid unnecessary endian conversion

use the local variable that already have the converted values.

No functional change in this patch.

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Link: https://lore.kernel.org/r/20230809053512.350660-2-aneesh.kumar@linux.ibm.com


Signed-off-by: Dave Jiang <dave.jiang@intel.com>