fibmap: include f2fs_fs.h before other header files

fibmap: include f2fs_fs.h before other header files

GCC 7.2.0 is unhappy with the usage of major/minor:

fibmap.c: In function ‘print_stat’:
fibmap.c:70:13: warning: In the GNU C Library, "major" is defined
 by <sys/sysmacros.h>. For historical compatibility, it is
 currently defined by <sys/types.h> as well, but we plan to
 remove this soon. To use "major", include <sys/sysmacros.h>
 directly. If you did not intend to use a system-defined macro
 "major", you should undefine it after including <sys/types.h>.
  printf("dev       [%d:%d]\n", major(st->st_dev), minor(st->st_dev));
             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This is because config.h is not included first, as a result, macros
defined in config.h is not recognized. So let's include f2fs_fs.h
before other header files.

Signed-off-by: Sheng Yong <shengyong1@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>