macserial problem on headless servers with kernel 2.4.17

["Eric C. Cooper" <ecc@cmu.edu>]

When I tried to run a 2.4.17 kernel on my headless Cube, the boot
sequence would hang after detecting the serial port:
    PowerMac Z8530 serial driver version 2.0
    tty00 at 0xfc72d020 (irq = 22) is a Z8530 ESCC 
              (hangs with no newline printed here ^)

(I have a Griffin CubePort instead of the internal modem on ttyS0.)
When I traced through macserial.c, I found the problem: it was calling
set_scc_power to disable the port.  But that logic is broken when
you're running headless; IMO it should be disabled by
CONFIG_SERIAL_CONSOLE.

As a workaround, I enabled CONFIG_XMON, which also bypasses this
"feature" in macserial.c.

Also, I noticed that the "is_cons" field in the mac_serial struct is
checked, but there is no logic for setting it to 1 anywhere.

-- 
Eric C. Cooper          e c c @ c m u . e d u