staging/lustre: remove empty file libcfs/linux/linux-sync.c

It was emptied by coan. So we no longer need it.

Signed-off-by: Peng Tao <tao.peng@emc.com>
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>