libnvdimm: fix the clear-error check in nsio_rw_bytes

A leftover from the 'bandaid' fix that disabled BTT error clearing in
rw_bytes resulted in an incorrect check. After we converted these checks
over to use the NVDIMM_IO_ATOMIC flag, the ndns->claim check was both
redundant, and incorrect. Remove it.

Fixes: 3ae3d67b ("libnvdimm: add an atomic vs process context flag to rw_bytes")
Cc: <stable@vger.kernel.org>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>