can: ti_hecc: add fifo overflow error reporting

When the rx FIFO overflows the ti_hecc would silently drop them since
the overwrite protection is enabled for all mailboxes. So disable it for
the lowest priority mailbox and return a proper error value when receive
message lost is set. Drop the message itself in that case, since it
might be partially updated.

Signed-off-by: Jeroen Hofstee <jhofstee@victronenergy.com>
Acked-by: Jeroen Hofstee <jhofstee@victronenergy.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>