gpio: slg7xl45106: Add support for slg7xl45106 i2c gpo expander

slg7xl45106 is i2c based 8-bit gpo expander, gpo pins are set and get by
writing and reading corresponding gpo bit value into its data register.

Signed-off-by: T Karthik Reddy <t.karthik.reddy@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Heiko Schocher <hs@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Link: https://lore.kernel.org/r/839f475cc75c97ffb3496a4caa93de2faabdbca2.1645629688.git.michal.simek@xilinx.com
diff --git a/MAINTAINERS b/MAINTAINERS
index 0f39bc6..bb6ea06 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -636,6 +636,7 @@
 F:	drivers/clk/clk_zynqmp.c
 F:	driver/firmware/firmware-zynqmp.c
 F:	drivers/fpga/zynqpl.c
+F:	drivers/gpio/gpio_slg7xl45106.c
 F:	drivers/gpio/zynq_gpio.c
 F:	drivers/gpio/zynqmp_gpio_modepin.c
 F:	drivers/i2c/i2c-cdns.c