PCI: pcie-check-and-return-bus_register-errors fix

__must_check goes on the declaration, not the definition.

Cc: "Randy.Dunlap" <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>