usb: dwc3: Makefile: Make dwc3 driver compile in u-boot

Now that the entire dwc3 driver is adapted to compile with uboot build,
modify the Makefiles so that the dwc3 driver can be built.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Reviewed-by: Lukasz Majewski <l.majewski@samsung.com>
diff --git a/Makefile b/Makefile
index 950c960..0f7d583 100644
--- a/Makefile
+++ b/Makefile
@@ -650,8 +650,10 @@
 libs-$(CONFIG_FMAN_ENET) += drivers/net/fm/
 libs-$(CONFIG_SYS_FSL_DDR) += drivers/ddr/fsl/
 libs-y += drivers/serial/
+libs-y += drivers/usb/dwc3/
 libs-y += drivers/usb/eth/
 libs-y += drivers/usb/gadget/
+libs-y += drivers/usb/gadget/udc/
 libs-y += drivers/usb/host/
 libs-y += drivers/usb/musb/
 libs-y += drivers/usb/musb-new/