Input: ili210x - do not retrieve/print chip firmware version

The driver's method to retrieve the firmware version on ili2117/
ili2118 chip flavours is incorrect. The firmware version register
address and layout are wrong.

The firmware version is not actually used anywhere inside or
outside this driver. There is a dev_dbg() print, but that is
only visible when the developer explicitly compiles in debug
support.

Don't make the code more complicated to preserve a feature that
no-one is using. Remove all code associated with chip firmware
version.

Signed-off-by: Sven Van Asbroeck <TheSven73@gmail.com>
Link: https://lore.kernel.org/r/20191112164429.11225-1-TheSven73@gmail.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>