linux-firmware: ixp4xx: Add the IXP4xx firmware

This firmware has been used since the early 2000s by OpenWrt and different PDA/SBC projects such as Linux handhelds for supporting the Network Processing Engines inside the Intel XScale IXP4xx SoC.

It is better to distribute it inside linux-firmware.

When distributions package the firmware they need to run the small C program that converts the distributable to a binary file, so I have added this small header file and a Makefile that shows how this works.

Signed-off-by: Linus Walleij linus.walleij@linaro.org