ARM: stm32: Add USB host boot support

Add support for booting from USB pen drive, since USB host port is
available on the STM32MP1.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Patrice Chotard <patrice.chotard@foss.st.com>
Cc: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
diff --git a/include/configs/stm32mp1.h b/include/configs/stm32mp1.h
index c553928..36e4004 100644
--- a/include/configs/stm32mp1.h
+++ b/include/configs/stm32mp1.h
@@ -102,11 +102,18 @@
 #define BOOT_TARGET_UBIFS(func)
 #endif
 
+#ifdef CONFIG_USB
+#define BOOT_TARGET_USB(func)	func(USB, usb, 0)
+#else
+#define BOOT_TARGET_USB(func)
+#endif
+
 #define BOOT_TARGET_DEVICES(func)	\
 	BOOT_TARGET_MMC1(func)		\
 	BOOT_TARGET_UBIFS(func)		\
 	BOOT_TARGET_MMC0(func)		\
 	BOOT_TARGET_MMC2(func)		\
+	BOOT_TARGET_USB(func)		\
 	BOOT_TARGET_PXE(func)
 
 /*