Fix new kernel-doc warning in mm/filemap.c:

  Warning(mm/filemap.c:2600): Excess function parameter 'ppos' description in '__generic_file_aio_write'
Signed-off-by: NRandy Dunlap <rdunlap@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>