comedi: vmk80xx: fix expression for tx buffer size

stable inclusion
from stable-v4.19.249
commit 8b65a17d21412bd20e04d110b0e4bfed1ff0cb80
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9RD17
CVE: CVE-2021-47475

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8b65a17d21412bd20e04d110b0e4bfed1ff0cb80



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

commit 242439f7 upstream.

The expression for setting the size of the allocated bulk TX buffer
(`devpriv->usb_tx_buf`) is calling `usb_endpoint_maxp(devpriv->ep_rx)`,
which is using the wrong endpoint (should be `devpriv->ep_tx`).  Fix it.

Fixes: a23461c4 ("comedi: vmk80xx: fix transfer-buffer overflow")
Cc: Johan Hovold <johan@kernel.org>
Cc: stable@vger.kernel.org # 4.9+
Reviewed-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20220607171819.4121-1-abbotti@mev.co.uk


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Cai Xinchen <caixinchen1@huawei.com>