PNP: add CONFIG_PNP_DEBUG_MESSAGES and pnp_dbg()

This adds the core function pnp_dbg() and a new config option to
enable it.

The PNP core debugging messages can be enabled at boot-time with the
"pnp.debug" kernel parameter.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 1150444..7164d4e 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1660,6 +1660,10 @@
 			Override pmtimer IOPort with a hex value.
 			e.g. pmtmr=0x508
 
+	pnp.debug	[PNP]
+			Enable PNP debug messages.  This depends on the
+			CONFIG_PNP_DEBUG_MESSAGES option.
+
 	pnpacpi=	[ACPI]
 			{ off }