tomoyo: fix timestamping for y2038

tomoyo: fix timestamping for y2038

Tomoyo uses an open-coded version of time_to_tm() to create a timestamp
from the current time as read by get_seconds(). This will overflow and
give wrong results on 32-bit systems in 2038.

To correct this, this changes the code to use ktime_get_real_seconds()
and the generic time64_to_tm() function that are both y2038-safe.
Using the library function avoids adding an expensive 64-bit division
in this code and can benefit from any optimizations we do in common
code.

Acked-by: Tetsuo Handa <[email protected]>
Signed-off-by: Arnd Bergmann <[email protected]>
Signed-off-by: James Morris <[email protected]>