The new cs5535-* drivers use PCI header config info rather than MSRs to
determine the memory region to use for things like GPIOs and MFGPTs. As
anticipated, we've run into a buggy BIOS:
This is a Soekris board, and its BIOS sets the size of the PCI ISA bridge
device's BAR0 to 8k. In reality, it should be 8 bytes (BAR0 is used for
SMBus stuff). This quirk checks for an incorrect size, and resets it
accordingly.