headers_check fix: linux/reinserfs_fs.h

fix the following 'make headers_check' warnings:

  usr/include/linux/reiserfs_fs.h:687: extern's make no sense in userspace
  usr/include/linux/reiserfs_fs.h:995: extern's make no sense in userspace
  usr/include/linux/reiserfs_fs.h:997: extern's make no sense in userspace
  usr/include/linux/reiserfs_fs.h:1467: extern's make no sense in userspace
  usr/include/linux/reiserfs_fs.h:1760: extern's make no sense in userspace
  usr/include/linux/reiserfs_fs.h:1764: extern's make no sense in userspace
  usr/include/linux/reiserfs_fs.h:1766: extern's make no sense in userspace
  usr/include/linux/reiserfs_fs.h:1769: extern's make no sense in userspace
  usr/include/linux/reiserfs_fs.h:1771: extern's make no sense in userspace
  usr/include/linux/reiserfs_fs.h:1805: extern's make no sense in userspace
  usr/include/linux/reiserfs_fs.h:1948: extern's make no sense in userspace
  usr/include/linux/reiserfs_fs.h:1949: extern's make no sense in userspace
  usr/include/linux/reiserfs_fs.h:1950: extern's make no sense in userspace
  usr/include/linux/reiserfs_fs.h:1951: extern's make no sense in userspace
  usr/include/linux/reiserfs_fs.h:1962: extern's make no sense in userspace
  usr/include/linux/reiserfs_fs.h:1963: extern's make no sense in userspace
  usr/include/linux/reiserfs_fs.h:1964: extern's make no sense in userspace

Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@gmail.com>