scsi: zfcp: auto variables for dereferenced structs in open port handler

Introduce automatic variables for adapter and QTCB bottom in
zfcp_fsf_open_port_handler(). This facilitates subsequent changes to meet
the 80 character per line limit.

Link: https://lore.kernel.org/r/20200312174505.51294-6-maier@linux.ibm.com
Reviewed-by: Fedor Loshakov <loshakov@linux.ibm.com>
Reviewed-by: Steffen Maier <maier@linux.ibm.com>
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Jens Remus <jremus@linux.ibm.com>
Signed-off-by: Steffen Maier <maier@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>