MFC r261915:

Under sys/netpfil/ipfw, surround two IPv6-specific static functions with
#ifdef INET6, since they are unused when INET6 is disabled.
MFC r261914:

In sys/fs/nandfs/nandfs_vfsops.c, #if 0 an unused static function.
MFC r261916:

In sys/dev/xen/console/console.c, #if 0 an unused static function.
MFC r261977:

In sys/dev/usb/controller/musb_otg.c, fix a warning about musbotg_odevd
being unused, by adding it to the part that handles getting descriptors.

Reviewed by:	hselasky
allow building without INET