staging/lustre/lnet: remove empty file lnet/lnet/api-errno.c

The file is empty. We can just remove it.

Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-2335
Lustre-change: http://review.whamcloud.com/5880


Reviewed-by: Liang Zhen <liang.zhen@intel.com>
Reviewed-by: Li Wei <wei.g.li@intel.com>
Reviewed-by: Isaac Huang <he.huang@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
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>