8250-men-mcb: fix error checking when get_num_ports returns -ENODEV

[ Upstream commit f50b6805dbb993152025ec04dea094c40cc93a0c ]

The current checking for failure on the number of ports fails when
-ENODEV is returned from the call to get_num_ports. Fix this by making
num_ports and loop counter i signed rather than unsigned ints. Also
add check for num_ports being less than zero to check for -ve error
returns.

Addresses-Coverity: ("Unsigned compared against 0")
Fixes: e2fea54e ("8250-men-mcb: add support for 16z025 and 16z057")
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Reviewed-by: NMichael Moese <mmoese@suse.de>
Link: https://lore.kernel.org/r/20191013220016.9369-1-colin.king@canonical.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/tty/serial/8250/8250_men_mcb.c

@@ -71,8 +71,8 @@ static int serial_8250_men_mcb_probe(struct mcb_device *mdev,
 {
 	struct serial_8250_men_mcb_data *data;
 	struct resource *mem;
-	unsigned int num_ports;
-	unsigned int i;
+	int num_ports;
+	int i;
 	void __iomem *membase;
 
 	mem = mcb_get_resource(mdev, IORESOURCE_MEM);
@@ -87,7 +87,7 @@ static int serial_8250_men_mcb_probe(struct mcb_device *mdev,
 	dev_dbg(&mdev->dev, "found a 16z%03u with %u ports\n",
 		mdev->id, num_ports);
 
-	if (num_ports == 0 || num_ports > 4) {
+	if (num_ports <= 0 || num_ports > 4) {
 		dev_err(&mdev->dev, "unexpected number of ports: %u\n",
 			num_ports);
 		return -ENODEV;
@@ -132,7 +132,7 @@ static int serial_8250_men_mcb_probe(struct mcb_device *mdev,
 
 static void serial_8250_men_mcb_remove(struct mcb_device *mdev)
 {
-	unsigned int num_ports, i;
+	int num_ports, i;
 	struct serial_8250_men_mcb_data *data = mcb_get_drvdata(mdev);
 
 	if (!data)