This patch adds driver support for the zynqmp modepin GPIO controller.
GPIO modepin driver set and get the value and status of the PS_MODE pin,
based on device-tree pin configuration. These four mode pins are
configurable as input/output. The mode pin has a control register, which
have lower four-bits [0:3] are configurable as input/output, next four-bits
can be used for reading the data  as input[4:7], and next setting the
output pin state output[8:11]. By default value of mode pin register is 0.
Signed-off-by: Piyush Mehta <piyush.mehta@xilinx.com>
Acked-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>