qdev: Fix memory leak in function set_pci_devfn Valgrind reported this memory leak which occured very often. Test scenario: qemu-system-i386 (no arguments), only BIOS started, terminate with monitor command (quit). v2: Use error_free instead of g_free (hint from Andreas Färber, thanks). Signed-off-by: Stefan Weil <sw@weilnetz.de> Acked-by: Andreas Färber <afaerber@suse.de>