uio: Fix return value of poll

The return type of __poll_t can't be negative,
-EIO will be translate to __poll_t,and will return to caller.

Fixes: beafc54 ("UIO: Add the User IO core code")
Signed-off-by: Angus Chen <angus.chen@jaguarmicro.com>
Link: https://lore.kernel.org/r/20241126124259.1367-1-angus.chen@jaguarmicro.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/uio/uio.c

@@ -565,7 +565,7 @@ static __poll_t uio_poll(struct file *filep, poll_table *wait)
 
 	mutex_lock(&idev->info_lock);
 	if (!idev->info || !idev->info->irq)
-		ret = -EIO;
+		ret = EPOLLERR;
 	mutex_unlock(&idev->info_lock);
 
 	if (ret)