gpio: Add driver for TI PCF8575 I2C GPIO expander

TI's PCF8575 is a 16-bit I2C GPIO expander.The device features a
16-bit quasi-bidirectional I/O ports. Each quasi-bidirectional I/O can
be used as an input or output without the use of a data-direction
control signal. The I/Os should be high before being used as inputs.
Read the device documentation for more details[1].

This driver is based on pcf857x driver available in Linux v4.7 kernel.
It supports basic reading and writing of gpio pins.

[1] http://www.ti.com/lit/ds/symlink/pcf8575.pdf

Signed-off-by: Vignesh R <vigneshr@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Mugunthan V N <mugunthanvnm@ti.com>
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 73b862d..64cf221 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -79,6 +79,13 @@
 	  Power and reset buttons are placed in "pm8916_key" bank and
           have gpio numbers 0 and 1 respectively.
 
+config PCF8575_GPIO
+	bool "PCF8575 I2C GPIO Expander driver"
+	depends on DM_GPIO && DM_I2C
+	help
+	 Support for PCF8575 I2C 16-bit GPIO expander. Most of these
+	 chips are from NXP and TI.
+
 config ROCKCHIP_GPIO
 	bool "Rockchip GPIO driver"
 	depends on DM_GPIO