staging: rtl8712: fix use after free bugs

stable inclusion
from stable-v5.10.142
commit 19e3f69d19801940abc2ac37c169882769ed9770
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I63OIO
CVE: CVE-2022-4095

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=19e3f69d19801940abc2ac37c169882769ed9770



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

_Read/Write_MACREG callbacks are NULL so the read/write_macreg_hdl()
functions don't do anything except free the "pcmd" pointer.  It
results in a use after free.  Delete them.

Fixes: 2865d42c ("staging: r8712u: Add the new driver to the mainline kernel")
Cc: stable <stable@kernel.org>
Reported-by: Zheng Wang <hackerzheng666@gmail.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/Yw4ASqkYcUhUfoY2@kili


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Guan Jing <guanjing6@huawei.com>
Reviewed-by: Chen Hui <judy.chenhui@huawei.com>
Reviewed-by: Zhang Qiao <zhangqiao22@huawei.com>
Reviewed-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>