PNP: notice whether we have PNP devices (PNPBIOS or PNPACPI)

PNP: notice whether we have PNP devices (PNPBIOS or PNPACPI)

This series converts i386 and x86_64 legacy serial ports to be platform
devices and prevents probing for them if we have PNP.

This prevents double discovery, where a device was found both by the legacy
probe and by 8250_pnp.

This also prevents the serial driver from claiming IRDA devices (unless they
have a UART PNP ID).  The serial legacy probe sometimes assumed the wrong IRQ,
so the user had to use "setserial" to fix it.

Removing the need for setserial to make IRDA devices work seems good, but it
does break some things.  In particular, you may need to keep setserial from
poking legacy UART stuff back in by doing something like "dpkg-reconfigure
setserial" with the "kernel" option.  Otherwise, the setserial-discovered
"UART" will claim resources and prevent the IRDA driver from loading.

This patch:

If we can discover devices using PNP, we can skip some legacy probes.  This
flag ("pnp_platform_devices") indicates that PNPBIOS or PNPACPI is enabled and
should tell us about builtin devices.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Keith Owens <kaos@ocs.com.au>
Cc: Len Brown <lenb@kernel.org>
Cc: Adam Belay <ambx1@neo.rr.com>
Cc: Matthieu CASTET <castet.matthieu@free.fr>
Cc: Jean Tourrilhes <jt@hpl.hp.com>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Ville Syrjala <syrjala@sci.fi>
Cc: Russell King <rmk+serial@arm.linux.org.uk>
Cc: Samuel Ortiz <samuel@sortiz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>