can: pcan_usb_core: remove obsolete variable open_time

The variable open_time in the struct peak_usb_device was used to protect
peak_usb_set_mode() only to be called, if the interface is up. Now the CAN
device infrastructure takes care of this.

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

diff --cc drivers/net/can/usb/peak_usb/pcan_usb_core.c
Simple merge

diff --cc drivers/net/can/usb/peak_usb/pcan_usb_core.h
Simple merge