[PATCH] SERIAL: allow shared 8250_pnp interrupts

PNP devices can use shared interrupts, so check to see whether we'll need
SA_SHIRQ for request_irq().

The builtin PDH UART on the HP rx8640 is an example of an ACPI/PNP device
that uses a shareable level-triggered, active-low interrupt.  The interrupt
can be shared in very large I/O configurations or by artificially lowering
IA64_DEF_LAST_DEVICE_VECTOR.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Adam Belay <ambx1@neo.rr.com>
Cc: Matthieu Castet <castet.matthieu@free.fr>
Cc: Li Shaohua <shaohua.li@intel.com>
Cc: Len Brown <len.brown@intel.com>
Acked-by: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>