RS-232 cable

Hello!

Okay, now that thanks to Jamey it is 100% known that GPIO4 works
independently of RS-232 power, I have re-enabled the cable detection IRQ
in h2200.c. I've added a printk() to the IRQ handler so that you can see
if it works (if you're able to use the framebuffer console, you may try
to boot without the console= kernel option and see these printk's on the
screen). Please try to insert/remove the serial cable, it should disable
RS-232 power when the cable is unplugged and power on when it is
plugged back.

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Greetings,
   Andrew