sc16is7xx: Read the LSR register for basic device presence check
Currently, the driver probes just fine and binds all its resources even if the physical device is not present. As the device lacks an identification register, let's at least read the LSR register to check whether a device at the configured address responds to the request at all. Signed-off-by: Daniel Mack <daniel@zonque.org> Link: https://lore.kernel.org/r/20200521091152.404404-7-daniel@zonque.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>