net: stmmac: ensure jumbo_frm error return is correctly checked for -ve value

[ Upstream commit 594238158bf748c285f0a73222cd9b7ccf3c525d ]

The current comparison of entry < 0 will never be true since entry is an
unsigned integer. Make entry an int to ensure -ve error return values
from the call to jumbo_frm are correctly being caught.

Detected by CoverityScan, CID#1238760 ("Macro compares unsigned to 0")

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 0df7186..65ed02b 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -2199,7 +2199,8 @@
 	unsigned int nopaged_len = skb_headlen(skb);
 	int i, csum_insertion = 0, is_jumbo = 0;
 	int nfrags = skb_shinfo(skb)->nr_frags;
-	unsigned int entry, first_entry;
+	int entry;
+	unsigned int first_entry;
 	struct dma_desc *desc, *first;
 	unsigned int enh_desc;
 	unsigned int des;