aha152x bugfix (1460 pccard, powerpc linux-2.4.12)

Hi Jürgen.

Thank you very much for your aha52x driver which has been very
useful for me on my i386 notebook.

Now I'm riding PowerPC and while resolving a portability issue,
I came across a bug in the driver. Suggestions for solving the
problems are attached. The patch header also contains some
comments.

1) The PPC has more than 16 IRQs. This resulted in an overflow
   of a static table. The fix replaces the 'aha152x_host[NUM_IRQS]'
   by 'aha152x_host[MAX_HOSTS]' (MAX_HOSTS is currently limited to 
   2 anyway).

2) Due to 1) the driver didn't work properly and resulting in
   the routine aha152x_device_reset() timing out. In this case,
   however, the driver failed to remove the command from the
   ISSUE_SC queue which eventually crashed the system.

3) minor stuff.

4) I also have a question: Your driver allocates its IRQ with the
   SA_SHIRQ flag set. However, I can't see how the ISR actually
   implements IRQ sharing. I.e. shouldn't it check all known
   hosts to find out who (if any) actually rose the IRQ?

Thanks for the great work.

Regards

-- Till