spl: common: Support for USB MSD FAT image loading

Add SPL support to be able to detect a USB Mass Storage device
connected to a USB host.  Once a USB Mass storage device is detected
the SPL will load the u-boot.img from a FAT partition to target address.

Signed-off-by: Dan Murphy <dmurphy@ti.com>
diff --git a/common/Makefile b/common/Makefile
index d12cba5..4d99ecd 100644
--- a/common/Makefile
+++ b/common/Makefile
@@ -197,6 +197,10 @@
 obj-$(CONFIG_SPL_ENV_SUPPORT) += env_attr.o
 obj-$(CONFIG_SPL_ENV_SUPPORT) += env_flags.o
 obj-$(CONFIG_SPL_ENV_SUPPORT) += env_callback.o
+ifdef CONFIG_SPL_USB_HOST_SUPPORT
+obj-$(CONFIG_SPL_USB_SUPPORT) += usb.o usb_hub.o
+obj-$(CONFIG_USB_STORAGE) += usb_storage.o
+endif
 ifneq ($(CONFIG_SPL_NET_SUPPORT),y)
 obj-$(CONFIG_ENV_IS_NOWHERE) += env_nowhere.o
 obj-$(CONFIG_ENV_IS_IN_MMC) += env_mmc.o