IB/srp: Remove !ch->target tests from the reconnect code

Remove the !ch->target tests from the reconnect code. These
tests are not needed: upon entry of srp_rport_reconnect()
it is guaranteed that all ch->target pointers are non-NULL.
None of the functions srp_new_cm_id(), srp_finish_req(),
srp_create_ch_ib() nor srp_connect_ch() modifies this pointer.
srp_free_ch_ib() is never called concurrently with
srp_rport_reconnect().

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Cc: Sebastian Parschauer <sebastian.riemer@profitbricks.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>