NFC: st21nfca: Fix logic when setting session_id

If dev_num >= ST21NFCA_NUM_DEVICES, the driver was returning an incorrect
success return code.

Once dev_num is set, it was not stated as busy.
Signed-off-by: Christophe Ricard <christophe-h.ricard@st.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/nfc/st21nfca/st21nfca.c

@@ -905,8 +905,11 @@ int st21nfca_hci_probe(void *phy_id, struct nfc_phy_ops *phy_ops,
 	 * persistent info to discriminate 2 identical chips
 	 */
 	dev_num = find_first_zero_bit(dev_mask, ST21NFCA_NUM_DEVICES);
+
 	if (dev_num >= ST21NFCA_NUM_DEVICES)
-		goto err_alloc_hdev;
+		return -ENODEV;
+
+	set_bit(dev_num, dev_mask);
 
 	scnprintf(init_data.session_id, sizeof(init_data.session_id), "%s%2x",
 		  "ST21AH", dev_num);