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/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 522dfc1..a9e9b30 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -550,4 +550,12 @@
 	help
 	  Support GPIO access on Kontron sl28cpld board management controllers.
 
+config SLG7XL45106_I2C_GPO
+	bool "slg7xl45106 i2c gpo expander"
+	depends on DM_GPIO
+	help
+	   Support for slg7xl45106 i2c gpo expander. It is an i2c based
+	   8-bit gpo expander, all gpo lines are controlled by writing
+	   value into data register.
+
 endif