icE1usb fw: Use #define's in descriptors for interface/endpoints ID

This way they can be used in other parts of the code more easily.

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
Change-Id: I565d9a43bc26b99bc385b46522e7da6a207b2412
diff --git a/firmware/ice40-riscv/icE1usb/Makefile b/firmware/ice40-riscv/icE1usb/Makefile
index 1c92edb..a8d18c9 100644
--- a/firmware/ice40-riscv/icE1usb/Makefile
+++ b/firmware/ice40-riscv/icE1usb/Makefile
@@ -48,6 +48,7 @@
 	config.h \
 	e1.h \
 	misc.h \
+	usb_desc_ids.h \
 	usb_str_app.gen.h \
 	$(NULL)