dt-bindings: input/touchscreen: Add compatible for IST3038B

Imagis IST3038B is a variant (firmware?) of Imagis IST3038 IC
differing from IST3038C in its register interface. Add the
compatible for it to the IST3038C bindings.

Signed-off-by: Markuss Broks <markuss.broks@gmail.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
[balejk@matfyz.cz: elaborate chip differences in the commit message]
Signed-off-by: Karel Balej <balejk@matfyz.cz>
Link: https://lore.kernel.org/r/20240301164659.13240-3-karelb@gimli.ms.mff.cuni.cz
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>