asix: fix uninit-value in asix_mdio_read()

mainline inclusion
from mainline-v5.16-rc7
commit 8035b1a2
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I95RDW
CVE: CVE-2021-47101

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=8035b1a2a37a29d8c717ef84fca8fe7278bc9f03



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

asix_read_cmd() may read less than sizeof(smsr) bytes and in this case
smsr will be uninitialized.

Fail log:
BUG: KMSAN: uninit-value in asix_check_host_enable drivers/net/usb/asix_common.c:82 [inline]
BUG: KMSAN: uninit-value in asix_check_host_enable drivers/net/usb/asix_common.c:82 [inline] drivers/net/usb/asix_common.c:497
BUG: KMSAN: uninit-value in asix_mdio_read+0x3c1/0xb00 drivers/net/usb/asix_common.c:497 drivers/net/usb/asix_common.c:497
 asix_check_host_enable drivers/net/usb/asix_common.c:82 [inline]
 asix_check_host_enable drivers/net/usb/asix_common.c:82 [inline] drivers/net/usb/asix_common.c:497
 asix_mdio_read+0x3c1/0xb00 drivers/net/usb/asix_common.c:497 drivers/net/usb/asix_common.c:497

Fixes: d9fe64e5 ("net: asix: Add in_pm parameter")
Reported-and-tested-by:  <syzbot+f44badb06036334e867a@syzkaller.appspotmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Link: https://lore.kernel.org/r/8966e3b514edf39857dd93603fc79ec02e000a75.1640117288.git.paskripkin@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Cheng Yu <serein.chengyu@huawei.com>