iot2050: Allow for more than 1 USB storage device

This was lost in refactoring while some users of the IOT2050 expect it
to work: Make sure that up to 3 USB storage devices are probed.

Fixes: 53873974a4 ("include: armv7: Enable distroboot across all configs")
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

include/configs/iot2050.h

@@ -15,6 +15,15 @@
 
 #include <configs/ti_armv7_common.h>
 
+/* allow up to 3 USB storage devices */
+#ifdef CONFIG_CMD_USB
+#undef BOOT_TARGET_USB
+#define BOOT_TARGET_USB(func) \
+	func(USB, usb, 0) \
+	func(USB, usb, 1) \
+	func(USB, usb, 2)
+#endif
+
 /*
  * This defines all MMC devices, even if the basic variant has no mmc1.
  * The non-supported device will be removed from the boot targets during