In tmpfs_chtimes(), remove checks on the nanosecond level when

In tmpfs_chtimes(), remove checks on the nanosecond level when
determining whether a node changed.

Other filesystems, e.g., UFS, only check on seconds, when determining
whether something changed.

This also corrects the birthtime case, where we checked tv_nsec
twice, instead of tv_sec and tv_nsec (PR).

PR:			201284
Submitted by:		David Binderman
Patch suggested by:	kib
Reviewed by:		kib
MFC after:		2 weeks
Committed from:		Essen FreeBSD Hackathon