rocker: remove trans parameter to rocker_cmd_exec function

The only purpose of passing this parameter is to check for
prepare phase. The only reason for a failure in that state is if
TLVs don't fit into descriptor. That is highly unlikely and if that
happens, it is a driver bug. So remove this parameter from
rocker_cmd_exec, and check for prepare phase in caller.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>