can: m_can: fix nominal bitiming tseg2 min for version >= 3.1

At lest the revision 3.3.0 of the bosch m_can IP core specifies that valid
register values for "Nominal Time segment after sample point (NTSEG2)" are from
1 to 127. As the hardware uses a value of one more than the programmed value,
mean tseg2_min is 2.

This patch fixes the tseg2_min value accordingly.

Cc: Dan Murphy <dmurphy@ti.com>
Cc: Mario Huettel <mario.huettel@gmx.net>
Acked-by: Sriram Dash <sriram.dash@samsung.com>
Link: https://lore.kernel.org/r/20201124190751.3972238-1-mkl@pengutronix.de
Fixes: b03cfc5b

 ("can: m_can: Enable M_CAN version dependent initialization")
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>