hw: reduce all i2c pullups from 10k

Currently testing the FMC_I2C bus with the https://gitlab.com/ohwr/project/fmc-dio-10i-8o FMC and the 10k pull-up resistors start to limit the bandwidth - it just about passes with the i2c-ocores configured for 400 kHz. See screenshot. I'd propose to change all pull-ups to a much lower value e.g. 2.2k.