fw/icE1usb: Import firmware for the icE1usb and icE1usb-proto boards

Currently only the icE1usb-proto is supported. Adaptation for the
final production hardware is yet to be done.

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/firmware/ice40-riscv/icE1usb/.gitignore b/firmware/ice40-riscv/icE1usb/.gitignore
new file mode 100644
index 0000000..5d5607c
--- /dev/null
+++ b/firmware/ice40-riscv/icE1usb/.gitignore
@@ -0,0 +1,5 @@
+*.elf
+*.hex
+*.bin
+*.o
+*.gen.h