usb: usbtmc: Fix erroneous wait_srq ioctl return

wait_event_interruptible_timeout returns a long
The return was being assigned to an int causing an integer overflow when
the remaining jiffies > INT_MAX resulting in random error returns.

Use a long return value,  converting to the int ioctl return only on
error.

Fixes: 739240a9 ("usb: usbtmc: Add ioctl USBTMC488_IOCTL_WAIT_SRQ")
Cc: stable@vger.kernel.org
Signed-off-by: Dave Penkler <dpenkler@gmail.com>
Link: https://lore.kernel.org/r/20250502070941.31819-3-dpenkler@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>