vfs: utimensat(): ignore tv_sec if tv_nsec == UTIME_OMIT or UTIME_NOW

The POSIX.1 draft spec for utimensat() says that if a times[n].tv_nsec field is UTIME_OMIT or UTIME_NOW, then the value in the corresponding tv_sec field is ignored. See the last sentence of this para, from the spec:

If the tv_nsec field of a timespec structure has the special value UTIME_NOW, the file's relevant timestamp shall be set to the greatest value supported by the file system that is not greater than the current time. If the tv_nsec field has the special value UTIME_OMIT, the file's relevant timestamp shall not be changed. In either case, the tv_sec field shall be ignored.

However the current Linux implementation requires the tv_sec value to be zero (or the EINVAL error results). This requirement should be removed.

@@ -169,14 +169,6 @@
 	if (utimes) {
 		if (copy_from_user(&tstimes, utimes, sizeof(tstimes)))
 			return -EFAULT;
-		if ((tstimes[0].tv_nsec == UTIME_OMIT ||
-		     tstimes[0].tv_nsec == UTIME_NOW) &&
-		    tstimes[0].tv_sec != 0)
-			return -EINVAL;
-		if ((tstimes[1].tv_nsec == UTIME_OMIT ||
-		     tstimes[1].tv_nsec == UTIME_NOW) &&
-		    tstimes[1].tv_sec != 0)
-			return -EINVAL;
 
 		/* Nothing to do, we must not even check the path.  */
 		if (tstimes[0].tv_nsec == UTIME_OMIT &&