can: xilinx_can: xcan_set_bittiming(): fix the data phase btr1 calculation

While calculating bitrate for the data phase, the driver is using phase
segment 1 of the arbitration phase instead of the data phase.

Fixes: c223da68

 ("can: xilinx_can: Add support for CANFD FD frames")
Signed-off-by: Appana Durga Kedareswara rao <appana.durga.rao@xilinx.com>
Signed-off-by: Srinivas Neeli <srinivas.neeli@xilinx.com>
Acked-by: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>