can: gs_usb: gs_usb_receive_bulk_callback(): check actual_length before accessing...

can: gs_usb: gs_usb_receive_bulk_callback(): check actual_length before accessing data

The URB received in gs_usb_receive_bulk_callback() contains a struct
gs_host_frame. The length of the data after the header depends on the
gs_host_frame hf::flags and the active device features (e.g. time
stamping).

Introduce a new function gs_usb_get_minimum_length() and check that we have
at least received the required amount of data before accessing it. Only
copy the data to that skb that has actually been received.

Fixes: d08e973a77d1 ("can: gs_usb: Added support for the GS_USB CAN devices")
Link: https://patch.msgid.link/20251114-gs_usb-fix-usb-callbacks-v1-3-a29b42eacada@pengutronix.de
[mkl: rename gs_usb_get_minimum_length() -> +gs_usb_get_minimum_rx_length()]
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>