can: etas_es58x: replace es58x_device::rx_max_packet_size by usb_maxpacket()

The field rx_max_packet_size of struct es58x_device in nothing else
than usb_endpoint_descriptor::wMaxPacketSize and can be easily
retrieved using usb_maxpacket(). Also, rx_max_packet_size being used a
single time, there is no merit to cache it locally.

Remove es58x_device::rx_max_packet_size and rely on usb_maxpacket()
instead.

Link: https://lore.kernel.org/all/20220611162037.1507-2-mailhol.vincent@wanadoo.fr


Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>