jbd2: replace current_kernel_time64 with ktime equivalent

jbd2: replace current_kernel_time64 with ktime equivalent

jbd2 is one of the few callers of current_kernel_time64(), which
is a wrapper around ktime_get_coarse_real_ts64(). This calls the
latter directly for consistency with the rest of the kernel that
is moving to the ktime_get_ family of time accessors.

Reviewed-by: Andreas Dilger <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Signed-off-by: Arnd Bergmann <[email protected]>
Signed-off-by: Theodore Ts'o <[email protected]>