Input: Add MAINTAINERS entry for SiS i2c touch input driver

I am the author of this SiS touch driver, and willing to maintain and
develop it further.

Signed-off-by: Mika Penttilä <mika.penttila@nextfour.com>
Link: https://lore.kernel.org/r/20201007035108.58636-1-mika.penttila@nextfour.com


Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>