hfsplus: update timestamps on truncate()

hfsplus: update timestamps on truncate()

The vfs takes care of updating ctime and mtime on ftruncate(), but on
truncate() it must be done by the module.

This patch can be tested with xfstests generic/313.

Link: http://lkml.kernel.org/r/9beb0913eea37288599e8e1b7cec8768fb52d1b8.1539316825.git.ernesto.mnd.fernandez@gmail.com
Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
Reviewed-by: Vyacheslav Dubeyko <slava@dubeyko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>