orangefs: avoid time conversion function

The new orangefs code uses a helper function to read a time field to
its private structures from struct iattr. This will conflict with the
move to 64-bit timestamps in the kernel and is generally not necessary.

This replaces the conversion with a simple cast to time64_t that shows
what is going on. As the orangefs-internal representation already uses
64-bit timestamps, there should be no ambiguity to negative values,
and the cast ensures that we treat them as times before 1970 on both
32-bit and 64-bit architectures, rather than times after 2038. This
patch keeps that behavior.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Mike Marshall <hubcap@omnibond.com>