can: peak: fix potential bug in packet fragmentation

commit d8a243af1a68395e07ac85384a2740d4134c67f4 upstream.

In some rare conditions when running one PEAK USB-FD interface over
a non high-speed USB controller, one useless USB fragment might be sent.
This patch fixes the way a USB command is fragmented when its length is
greater than 64 bytes and when the underlying USB controller is not a
high-speed one.

Signed-off-by: Stephane Grosjean <s.grosjean@peak-system.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>