drivers: fmc-eeprom: Reset the pointer on error.

On error, set the slot->nvmem to NULL. This keeps the data structure in
line with the real status (the nvmem device was not found).

Reported by: Federico Vaga <federico.vaga@cern.ch>
Signed-off-by: Vaibhav Gupta <vaibhav.gupta@cern.ch>

drivers/fmc/fmc-eeprom.c

@@ -189,8 +189,11 @@ static int __fmc_slot_eeprom_add(struct fmc_slot *slot,
 		"%s", dev_name(&slot->eeprom->dev));
 	slot->nvmem = nvmem_device_find(nvmem_parent_name,
 					fmc_nvmem_device_find_match);
-	if (IS_ERR_OR_NULL(slot->nvmem))
-		return PTR_ERR(slot->nvmem);
+	if (IS_ERR_OR_NULL(slot->nvmem)) {
+		int err = PTR_ERR(slot->nvmem)
+		slot->nvmem = NULL;
+		return err;
+	}
 	kfree(nvmem_parent_name);
 #endif