zynqmp: gpio: Add support for zynqmp gpio modepin driver

ZynqMP modepin driver has capability to get/set/check status of modepin
gpios. These modepins are accessed using xilinx firmware. In modepin
register, [3:0] bits set direction, [7:4] bits read IO, [11:8] bits
set/clear IO.

Signed-off-by: T Karthik Reddy <t.karthik.reddy@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Link: https://lore.kernel.org/r/2d802d98fd56d95d764532a33e844d935e0cebb3.1635505900.git.michal.simek@xilinx.com
diff --git a/MAINTAINERS b/MAINTAINERS
index e718ad2..b3b5c1c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -602,6 +602,7 @@
 F:	driver/firmware/firmware-zynqmp.c
 F:	drivers/fpga/zynqpl.c
 F:	drivers/gpio/zynq_gpio.c
+F:	drivers/gpio/zynqmp_gpio_modepin.c
 F:	drivers/i2c/i2c-cdns.c
 F:	drivers/i2c/muxes/pca954x.c
 F:	drivers/i2c/zynq_i2c.c