nvme-cli: Increase size of ONTAP namespace path variable

nvme-cli: Increase size of ONTAP namespace path variable

nspath's size is ONTAP_NS_PATHLEN and is written to by:

snprintf(nspath, ONTAP_NS_PATHLEN, "%s%s%s%s", ontap_vol,
                        vol_name, "/", ns_name);

Required bytes:

- ontap_vol is a constant char pointer, set to "/vol/", so 5 bytes
- vol_name's size is ONTAP_LABEL_LEN, which is 260, deducting the
  null-byte for termination makes 259 required bytes
- "/" is 1 byte
- ns_name's size is also ONTAP_LABEL_LEN, which is 260, deducting
  the null-byte for termination makes 259 required bytes
- the final null-byte: 1

That makes in total 5 + 259 + 1 + 259 + 1 = 525 required bytes

Signed-off-by: Simon Schricker <sschricker@suse.de>