can: gs_usb: gs_can_open(): merge setting of timestamp flags and init

Merge the bodies of 2 consecutive "if (dev->feature &
GS_CAN_FEATURE_HW_TIMESTAMP)" statements.

Link: https://lore.kernel.org/all/20221019221016.1659260-4-mkl@pengutronix.de


Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>