I got this configuration up and running easily last week. The gateway has been running since then (Utrecht Noord-Oost, Holland), without the power block getting (too) warm.
I used a 5V 2A power block for the Raspberry Pi, with the Pi then powering the IC880A-SPI. I followed the instructions and the installation script (!!) at https://github.com/ttn-zh/ic880a-gateway/tree/spi (don't forget to select the spi branch).