can: rename can_try_module_get to can_get_proto

can_try_module_get does return a struct can_proto.
The name explains what is done in so much detail that a caller
may not notice that a struct can_proto is locked/unlocked.
Signed-off-by: NKurt Van Dijck <kurt.van.dijck@eia.be>
Acked-by: NOliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>