Convert the inode timestamp updates to use fat_truncate_time.

Link: http://lkml.kernel.org/r/2663d3083c4dd62f00b64612c8eaf5542bb05a4c.1538363961.git.sorenson@redhat.comSigned-off-by: NFrank Sorenson <sorenson@redhat.com>
Acked-by: NOGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>