firmware: send -EINTR on signal abort on fallback mechanism

Right now we send -EAGAIN to a syfs write which got interrupted.
Userspace can't tell what happened though, send -EINTR if we
were killed due to a signal so userspace can tell things apart.

This is only applicable to the fallback mechanism.

Reported-by: Martin Fuzzey <mfuzzey@parkeon.com>
Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/firmware_class.c

@@ -1089,9 +1089,12 @@ static int _request_firmware_load(struct firmware_priv *fw_priv,
 		mutex_unlock(&fw_lock);
 	}
 
-	if (fw_state_is_aborted(&buf->fw_st))
-		retval = -EAGAIN;
-	else if (buf->is_paged_buf && !buf->data)
+	if (fw_state_is_aborted(&buf->fw_st)) {
+		if (retval == -ERESTARTSYS)
+			retval = -EINTR;
+		else
+			retval = -EAGAIN;
+	} else if (buf->is_paged_buf && !buf->data)
 		retval = -ENOMEM;
 
 	device_del(f_dev);