fs: jfs: Replace CURRENT_TIME_SEC by current_time()

jfs uses nanosecond granularity for filesystem timestamps.
Only this assignment is not using nanosecond granularity.
Use current_time() to get the right granularity.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>