Input: tsc2004 - add support for tsc2004

This adds support for the i2c based tsc2004 touchscreen controller.

Signed-off-by: Michael Welling <mwelling@ieee.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>