configs: stm32mp15: Add usb_pgood_delay for ST boards

Add usb_pgood_delay to ensure a correct detection of USB devices.

Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
diff --git a/include/configs/stm32mp15_st_common.h b/include/configs/stm32mp15_st_common.h
index d0cd413..866cd7a 100644
--- a/include/configs/stm32mp15_st_common.h
+++ b/include/configs/stm32mp15_st_common.h
@@ -9,6 +9,7 @@
 #define __CONFIG_STM32MP15_ST_COMMON_H__
 
 #define STM32MP_BOARD_EXTRA_ENV \
+	"usb_pgood_delay=2000\0" \
 	"console=ttySTM0\0"
 
 #include <configs/stm32mp15_common.h>