firmware: use int16_t for recv_fps's return value

This fixes a bug with framerates above 127.

Signed-off-by: Martin Stensgård <mastensg@ping.uio.no>
software: debianize

Signed-off-by: Martin Stensgård <mastensg@ping.uio.no>
software/.gitignore: ignore generated debian files

Signed-off-by: Martin Stensgård <mastensg@ping.uio.no>