[media] em28xx: do not interpret eeprom content if eeprom key is invalid

If the eeprom key isn't valid, either a different (currently unknown) format
is used or the eeprom is corrupted.
In both cases it doesn't make sense to interpret the data.
Also print an error message.
Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/usb/em28xx/em28xx-i2c.c

@@ -434,8 +434,12 @@ static int em28xx_i2c_eeprom(struct em28xx *dev, unsigned char *eedata, int len)
 			printk("\n");
 	}
 
-	if (em_eeprom->id == 0x9567eb1a)
-		dev->hash = em28xx_hash_mem(eedata, len, 32);
+	if (em_eeprom->id != 0x9567eb1a) {
+		em28xx_errdev("Unknown eeprom type or eeprom corrupted !");
+		return -ENODEV;
+	}
+
+	dev->hash = em28xx_hash_mem(eedata, len, 32);
 
 	em28xx_info("EEPROM ID = 0x%08x, EEPROM hash = 0x%08lx\n",
 		    em_eeprom->id, dev->hash);