Revert "time: Handle negative seconds correctly in timespec64_to_ns()"

Revert "time: Handle negative seconds correctly in timespec64_to_ns()"

This reverts commit c6f9b7b6f19c0f664af75b8b418ec55bd155d616 which is
commit 39ff83f2f6cc5cc1458dfcea9697f96338210beb upstream.

Arnd reports that this needs more review before being merged into all of
the trees.

Link: https://lore.kernel.org/r/CAK8P3a0z5jE=Z3Ps5bFTCFT7CHZR1JQ8VhdntDJAfsUxSPCcEw@mail.gmail.com
Reported-by: Arnd Bergmann <arnd@kernel.org>
Cc: Lukas Hannen <lukas.hannen@opensource.tttech-industrial.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>