can: peak_usb: peak_usb_get_ts_time(): fix timestamp wrapping

Fabian Inostroza <fabianinostrozap@gmail.com> has discovered a potential
problem in the hardware timestamp reporting from the PCAN-USB USB CAN interface
(only), related to the fact that a timestamp of an event may precede the
timestamp used for synchronization when both records are part of the same USB
packet. However, this case was used to detect the wrapping of the time counter.

This patch details and fixes the two identified cases where this problem can
occur.

Reported-by: Fabian Inostroza <fabianinostrozap@gmail.com>
Signed-off-by: Stephane Grosjean <s.grosjean@peak-system.com>
Link: https://lore.kernel.org/r/20201014085631.15128-1-s.grosjean@peak-system.com
Fixes: bb478555

 ("can: usb: PEAK-System Technik USB adapters driver core")
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>