staging/lustre/libcfs: revert changes to libcfs_sock_ioctl

Changes introduced by 80db2734
unfortunately totally break lustre, we use this function
to access not only socket proto obs, but also device ioctl
like SIOCGIFCONF that now fail.
Reverting part of the previous patch to regain the needed
functionality.

Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
CC: Fredrick John Berchmans <fredrickprashanth@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>