ipmi:ssif: Only unregister the platform driver if it was registered

mainline inclusion
from mainline-5.2
commit 44f56a39
category: bugfix
bugzilla: NA
CVE: NA

-------------------------------------------------

Otherwise you will get an error when the driver is removed if you
set trydmi=0.
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Signed-off-by: NWenchao Hao <haowenchao@huawei.com>
Reviewed-by: NMiaohe Lin <linmiaohe@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/char/ipmi/ipmi_ssif.c

@@ -1972,7 +1972,8 @@ static void cleanup_ipmi_ssif(void)
 
 	kfree(ssif_i2c_driver.address_list);
 
-	platform_driver_unregister(&ipmi_driver);
+	if (ssif_trydmi)
+		platform_driver_unregister(&ipmi_driver);
 
 	free_ssif_clients();
 }