Add support for Microchip MCP23017 which is a 16-Bit I/O expander with I2c interface. Datasheet is available here: https://www.microchip.com/wwwproducts/en/MCP23017 Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com> Change-Id: I18d0add0d30970a3f08859f2cf38261f699056fd Reviewed-on: https://gerrit.st.com/c/mpu/oe/st/u-boot/+/190046 Reviewed-by: CITOOLS <MDG-smet-aci-reviews@list.st.com> Reviewed-by: CIBUILD <MDG-smet-aci-builds@list.st.com> Reviewed-by: Patrick DELAUNAY <patrick.delaunay@foss.st.com> Tested-by: Patrice CHOTARD <patrice.chotard@st.com> Tested-by: Patrick DELAUNAY <patrick.delaunay@foss.st.com>