pch_can: fix 800k comms issue

Currently, 800k comms fails since prop_seg set zero.
(EG20T PCH CAN register of prop_seg must be set more than 1)
To prevent prop_seg set to zero, change tseg2_min 1 to 2.

Signed-off-by: Tomoya MORINAGA <tomoya-linux@dsn.okisemi.com>
Signed-off-by: David S. Miller <davem@davemloft.net>