asix: fix wrong return value in asix_check_host_enable()

If asix_read_cmd() returns 0 on 30th interation, 0 will be returned from
asix_check_host_enable(), which is logically wrong. Fix it by returning
-ETIMEDOUT explicitly if we have exceeded 30 iterations

Also, replaced 30 with #define as suggested by Andrew

Fixes: a786e3195d ("net: asix: fix uninit value bugs")
Reported-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/ecd3470ce6c2d5697ac635d0d3b14a47defb4acb.1640117288.git.paskripkin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/usb/asix_common.c

@@ -9,6 +9,8 @@
 
 #include "asix.h"
 
+#define AX_HOST_EN_RETRIES	30
+
 int asix_read_cmd(struct usbnet *dev, u8 cmd, u16 value, u16 index,
 		  u16 size, void *data, int in_pm)
 {
@@ -68,7 +70,7 @@ static int asix_check_host_enable(struct usbnet *dev, int in_pm)
 	int i, ret;
 	u8 smsr;
 
-	for (i = 0; i < 30; ++i) {
+	for (i = 0; i < AX_HOST_EN_RETRIES; ++i) {
 		ret = asix_set_sw_mii(dev, in_pm);
 		if (ret == -ENODEV || ret == -ETIMEDOUT)
 			break;
@@ -83,7 +85,7 @@ static int asix_check_host_enable(struct usbnet *dev, int in_pm)
 			break;
 	}
 
-	return ret;
+	return i >= AX_HOST_EN_RETRIES ? -ETIMEDOUT : ret;
 }
 
 static void reset_asix_rx_fixup_info(struct asix_rx_fixup_info *rx)