KASAN: use-after-free Read in __smsc95xx_mdio_read

[syzbot]

syzbot suspects this issue was fixed by commit:

commit 7e23ab72e73bc601b4cf2983382691d9f165c8d1
Author: Ding Xiang <dingxiang at cmss.chinamobile.com>
Date:   Mon Mar 30 07:56:26 2020 +0000

    pinctrl: nomadik:remove unneeded variable

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=13cfe3a0900000
start commit:   7ae77150 Merge tag 'powerpc-5.8-1' of git://git.kernel.org..
git tree:       upstream
kernel config:  https://syzkaller.appspot.com/x/.config?x=d195fe572fb15312
dashboard link: https://syzkaller.appspot.com/bug?extid=a7ebdb01bb2cc165cab6
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17046c66100000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=140a8a3e100000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: pinctrl: nomadik:remove unneeded variable

For information about bisection process see: https://goo.gl/tpsmEJ#bisection