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.

Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>