staging: usbip: userspace: move sysfs_utils to libsrc

Since it offers a API to both usbip tools and libusbip,
it is more appropriate to be place in the library.

Signed-off-by: Valentina Manea <valentina.manea.m@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>