firmware/ice40-riscv: Create a reboot() function

instead of direct access to registers.

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
Change-Id: Iaee092c5ef651f0350b3f46386ed79fdbe06afcb
diff --git a/firmware/ice40-riscv/icE1usb/misc.h b/firmware/ice40-riscv/icE1usb/misc.h
index 6d90364..69c0da7 100644
--- a/firmware/ice40-riscv/icE1usb/misc.h
+++ b/firmware/ice40-riscv/icE1usb/misc.h
@@ -28,3 +28,5 @@
 
 void e1_led_set(bool enable, uint8_t cfg);
 uint16_t e1_tick_read(void);
+
+void reboot(int fw);