[SCSI] gdth: Remove gdth_ctr_tab[]

  - Places like Initialization and Reset that Just loop on all devices can
    use the link list with the list_for_each_entry macro.
    But the io_ctrl from user mode now suffers performance-wise because
    code has to do a sequential search for the requested host number.
    I have isolated this search in a gdth_find_ha(int hanum) member
    for future enhancement if needed.

Signed-off-by Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>