can: m_can: m_can_{read_fifo,echo_tx_event}(): shift timestamp to full 32 bits

In commit 1be37d3b ("can: m_can: fix periph RX path: use
rx-offload to ensure skbs are sent from softirq context") the RX path
for peripheral devices was switched to RX-offload.

Received CAN frames are pushed to RX-offload together with a
timestamp. RX-offload is designed to handle overflows of the timestamp
correctly, if 32 bit timestamps are provided.

The timestamps of m_can core are only 16 bits wide. So this patch
shifts them to full 32 bit before passing them to RX-offload.

Link: https://lore.kernel.org/all/20220612211410.4081390-1-mkl@pengutronix.de
Fixes: 1be37d3b

 ("can: m_can: fix periph RX path: use rx-offload to ensure skbs are sent from softirq context")
Cc: <stable@vger.kernel.org> # 5.13
Cc: Torin Cooper-Bennun <torin@maxiluxsystems.com>
Reviewed-by: Chandrasekar Ramakrishnan <rcsekar@samsung.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>