configs: stm32mp1: Enable BUTTON_GPIO flag for stm32mp15_defconfig

Enable BUTTON_GPIO flag for STM32MP15.

Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
diff --git a/configs/stm32mp15_defconfig b/configs/stm32mp15_defconfig
index 3302b30..ffe7512 100644
--- a/configs/stm32mp15_defconfig
+++ b/configs/stm32mp15_defconfig
@@ -69,6 +69,8 @@
 CONFIG_USE_SERVERIP=y
 CONFIG_SERVERIP="192.168.1.1"
 CONFIG_STM32_ADC=y
+CONFIG_BUTTON=y
+CONFIG_BUTTON_GPIO=y
 CONFIG_CLK_SCMI=y
 CONFIG_SET_DFU_ALT_INFO=y
 CONFIG_USB_FUNCTION_FASTBOOT=y