board: st: stm32mp135f_dk: align MCP230XX init prio to I2C

MCP230XX IO expander is interfaced via i2c hence it is
suffisant to align its init priority to the i2c one.

Signed-off-by: Alain Volmat <alain.volmat@foss.st.com>

Author: Alain Volmat

boards/st/stm32mp135f_dk/Kconfig.defconfig

@@ -0,0 +1,11 @@
+# STM32MP135F DISCOVERY board configuration
+
+# Copyright (c) 2025 STMicroelectronics
+# SPDX-License-Identifier: Apache-2.0
+
+if BOARD_STM32MP135F_DK
+
+config GPIO_MCP230XX_INIT_PRIORITY
+	default I2C_INIT_PRIORITY
+
+endif # BOARD_STM32MP135F_DK