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/drivers/pnp/core.c b/drivers/pnp/core.c
index 7cb1ffc..61291b5 100644
--- a/drivers/pnp/core.c
+++ b/drivers/pnp/core.c
@@ -221,3 +221,14 @@
 }
 
 subsys_initcall(pnp_init);
+
+int pnp_debug;
+
+#if defined(CONFIG_PNP_DEBUG_MESSAGES)
+static int __init pnp_debug_setup(char *__unused)
+{
+	pnp_debug = 1;
+	return 1;
+}
+__setup("pnp.debug", pnp_debug_setup);
+#endif