void z8530_write_port (unsigned long p, u8 d);
Write a value to a port with delays if need be. Note that the caller must hold locks to avoid read/writes from other contexts violating the 5uS rule
In the longer term this should become an architecture specific section so that this can become a generic driver interface for all platforms. For now we only handle PC I/O ports with or without the dread 5uS sanity delay.