iwlwifi: mvm: silence uninitialized variable warning

"max_amsdu_len" isn't set if kstrtouint() fails.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/debugfs.c b/drivers/net/wireless/intel/iwlwifi/mvm/debugfs.c
index 406cf1c..b344898 100644
--- a/drivers/net/wireless/intel/iwlwifi/mvm/debugfs.c
+++ b/drivers/net/wireless/intel/iwlwifi/mvm/debugfs.c
@@ -1020,6 +1020,8 @@
 	int ret;
 
 	ret = kstrtouint(buf, 0, &max_amsdu_len);
+	if (ret)
+		return ret;
 
 	if (max_amsdu_len > IEEE80211_MAX_MPDU_LEN_VHT_11454)
 		return -EINVAL;