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/Makefile b/drivers/gpio/Makefile
index 33f7d41..b2e78b0 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -72,3 +72,4 @@
 obj-$(CONFIG_MAX7320_GPIO)	+= max7320_gpio.o
 obj-$(CONFIG_SL28CPLD_GPIO)	+= sl28cpld-gpio.o
 obj-$(CONFIG_ZYNQMP_GPIO_MODEPIN)	+= zynqmp_gpio_modepin.o
+obj-$(CONFIG_SLG7XL45106_I2C_GPO)	+= gpio_slg7xl45106.o