staging: serqt_usb2: remove unneeded return in qt_unthrottle

this return is at the end of the void function qt_unthrottle, which is
not needed, and also remove the new line below this.

Signed-off-by: Devendra Naga <develkernel412222@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>