mlxsw: core: Add bus argument to environment init API

Pass bus argument to mlxsw_env_init(). The purpose is to get access to
device handle, which is to be provided to error message in case of line
card activation failure.

Signed-off-by: Vadim Pasternak <vadimp@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>