[SCSI] zfcp: remove unused references, declarations and flags

 - Remove unused references and declarations, including one instance
   of the FC ls_adisc struct that has been defined twice.
 - Also remove the flags COMMON_OPENING, COMMON_CLOSING,
   ADAPTER_REGISTERED and XPORT_OK that are only set and cleared, but
   not checked anywhere.
 - Remove the zfcp specific atomic_test_mask makro. Simply use
   atomic_read directly instead.
 - Remove the zfcp internal sg helper functions and switch the places
   where it is still used to call sg_virt directly.
 - With the update of the QDIO code, the QDIO data structures no
   longer use the volatile type qualifier. Now we can also remove the
   volatile qualifiers from the zfcp code.

Signed-off-by: Swen Schillig <swen@vnet.ibm.com>
Signed-off-by: Christof Schmitt <christof.schmitt@de.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>