ads7846 is a touch-screen controller that is an input device rather
than a display device, so move it to the hw/input folder.

Signed-off-by: Gan Qixin <ganqixin@huawei.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20201115123503.1110665-1-ganqixin@huawei.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>