MAINTAINERS: Remove Bjorn Helgaas as PNP maintainer

I don't have time or knowledge to add anything useful to PNP, so remove
myself from the PNP entry.
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

MAINTAINERS

@@ -6935,7 +6935,6 @@ F:	drivers/power/
 
 PNP SUPPORT
 M:	Rafael J. Wysocki <rafael.j.wysocki@intel.com>
-M:	Bjorn Helgaas <bhelgaas@google.com>
 S:	Maintained
 F:	drivers/pnp/