drivers:cap11xx-gpio: Add new gpiochip driver for the cap1293 tc

The driver is derived from the input cap11xx.c driver: drivers/input/keyboard/cap11xx.c Instead of providing an input device, the driver registers a gpiochip with a read-only line for each sensor-input. The led handling was kept commented in source so that it can be implemented if required. The driver has so far only been tested with the cap1293 chip.

Additional dt properties: disable-rf-filter: If set disables the RF noise filter delta-sense: Allows to set sensivity for all inputs, the value should be in range 0x00 to 0x07 (see reg 0x1f in datasheet) invert-gpio-output: If set inverts the gpioget output.

BCS 746-001576