ARM: dts: stm32: add mcp23017 IO expander on I2C1 on stm32mp135f-dk
MCP23017 is an IO expander offering 16 input/output port expander with
interrupt output.
On stm32mp135f-dk, only INTA is routed (on PG12), but MCP23017 can mirror
the bank B interrupts on INTA, that's why the property microchip,irq-mirror
is used.