dt-bindings: input: iqs7222: Define units for slider properties

The units assumed by the 'azoteq,top-speed', 'azoteq,bottom-speed'
and 'azoteq,gesture-dist' properties are unspecified; define them
according to the device's datasheet.

Signed-off-by: Jeff LaBundy <jeff@labundy.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/ZKrpMekZBt95Gmnr@nixie71


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