Describe the bug
Arduino shields fail to operate as the I2C bus has been moved from I2C1 to I2C3.

On the Arduino UNO pinout here: the I2C are on D18 and D19, which on the disco_l475_iot1 board is CN1 pins 9 and 10. and connected to I2C1.

This commit changes the pins to I2C3, which are on the analog pins of the Arduino Uno connector (CN4 on the Disco board)

To Reproduce
Build the LVGL demo for the Disco L475 board using the adafruit_2_8_tft_touch_v2 shield.

Note you need to reduce the amount of video memory allocated from 64% to about 14% to fit in RAM.

Expected behavior
Touching "Hello World" button resets the counter.

To fix
In disco_l475_iot1/arduino_r3_connector.dtsi:

Change line 38 from

arduino_i2c: &i2c3 {};

to

arduino_i2c: &i2c1 {};

Impact
All Arduino boards using the default I2C port fail to work.

Environment (please complete the following information):

• Windows 11 Home,
• Zephyr SDK 0.17.0
• Zephyr OS build v3.7.1-72-gbf440dec238c

Additional context

From Disco board schematic: