Add blacklisting capability to serial_pci to avoid misdetection of serial ports

The serial_pci driver tries to guess serial ports on unknown devices based
on the PCI class (modem or serial).  On certain softmodems (AC'97 modems)
this can lead to the recognition of non-existing serial ports.

This patch adds a blacklist of PCI IDs that are to be ignored by the driver.

[akpm@linux-foundation.org: cleanups]
Signed-off-by: Christian Schmidt <schmidt@digadd.de>
Cc: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Russell King <rmk+lkml@arm.linux.org.uk>
Cc: Yinghai Lu <yinghai.lu@sun.com>
Acked-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>