usb: potential integer overflow in usbg_make_tpg()

usb: potential integer overflow in usbg_make_tpg()

The variable tpgt in usbg_make_tpg() is defined as unsigned long and is
assigned to tpgt->tport_tpgt, which is defined as u16. This may cause an
integer overflow when tpgt is greater than USHRT_MAX (65535). I
haven't tried to trigger it myself, but it is possible to trigger it
by calling usbg_make_tpg() with a large value for tpgt.

I modified the type of tpgt to match tpgt->tport_tpgt and adjusted the
relevant code accordingly.

This patch is similar to commit 59c816c1f24d ("vhost/scsi: potential
memory corruption").

Signed-off-by: Chen Yufeng <chenyufeng@iie.ac.cn>
Link: https://lore.kernel.org/r/20250415065857.1619-1-chenyufeng@iie.ac.cn
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>