Fix erroneous claim of board.I2C() by deinited display.

At the end of a session that called displayio.release_displays() (and did not initialize a new display), a board.I2C() bus that was previously used by a display would wrongly be considered still in use. While I can’t think of any unrecoverable problem this would cause in the next session, it violates the assumption that a soft reboot resets everything not needed by displays, potentially leading to confusion.

By itself, this change does not fix the problem yet - rather, it introduces the same issue as in #3581 for SPI. This needs to be solved in the same way for I2C and SPI.

shared-module/board/__init__.c

@@ -139,7 +139,7 @@ void reset_board_busses(void) {
     bool display_using_i2c = false;
     #if CIRCUITPY_DISPLAYIO
     for (uint8_t i = 0; i < CIRCUITPY_DISPLAY_LIMIT; i++) {
-        if (displays[i].i2cdisplay_bus.bus == i2c_singleton) {
+        if (displays[i].bus_base.type == &displayio_i2cdisplay_type && displays[i].i2cdisplay_bus.bus == i2c_singleton) {
             display_using_i2c = true;
             break;
         }