[SCSI] scsi_dh_rdac: move the init code from rdac_activate to rdac_bus_attach

Moving the initialization code from rdac_activate to rdac_bus_attach which is
more efficient.  We don't have to collect all the information during every
activate.

Signed-off-by: Babu Moger <babu.moger@lsi.com>
Reviewed-by: Vijay Chauhan <vijay.chauhan@lsi.com>
Reviewed-by: Bob Stankey <Robert.stankey@lsi.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>