icE1usb fw: Internal API for configuring E1 rx/tx config register

Related: OS#4675
Change-Id: Ib23f9b99f169ab18d730bcf67b97a7b6bf863e98
diff --git a/firmware/ice40-riscv/icE1usb/e1.h b/firmware/ice40-riscv/icE1usb/e1.h
index c438cb9..05ce19a 100644
--- a/firmware/ice40-riscv/icE1usb/e1.h
+++ b/firmware/ice40-riscv/icE1usb/e1.h
@@ -11,6 +11,9 @@
 void e1_poll(void);
 void e1_debug_print(bool data);
 
+void e1_tx_config(uint16_t cr);
+void e1_rx_config(uint16_t cr);
+
 volatile uint8_t *e1_data_ptr(int mf, int frame, int ts);
 unsigned int e1_data_ofs(int mf, int frame, int ts);