staging: usbip: Fix build with --with-tcp-wrappers

With --with-tcp-wrappers=no specified, the build system reset LIBS to
the empty string and thus fails to link against libsysfs.
Signed-off-by: Dominik Paulus <dominik.paulus@fau.de>
Signed-off-by: Tobias Polzer <tobias.polzer@fau.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/usbip/userspace/configure.ac

@@ -70,7 +70,6 @@ AC_ARG_WITH([tcp-wrappers],
 		       [AC_MSG_RESULT([not found]); exit 1])
 	     else
 		     AC_MSG_RESULT([no]);
-		     LIBS="$saved_LIBS"
 	     fi],
 	    dnl [ACTION-IF-NOT-GIVEN]
 	    [AC_MSG_RESULT([(default)])