can: peak_usb: convert to use le32_add_cpu()

Convert cpu_to_le32(le32_to_cpu(E1) + E2) to use le32_add_cpu().

Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Link: https://lore.kernel.org/r/20200914041744.3701840-1-liushixin2@huawei.com


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