[SCSI] qla4xxx: Fix smatch warnings

Fix following smatch warnings:-
drivers/scsi/qla4xxx/ql4_os.c:6573
qla4xxx_sysfs_ddb_set_param() warn: possible memory leak of 'fw_ddb_entry'
drivers/scsi/qla4xxx/ql4_os.c:6596
qla4xxx_sysfs_ddb_delete() warn: variable dereferenced before check 'fnode_sess'
(see line 6584)
drivers/scsi/qla4xxx/ql4_os.c:6632
qla4xxx_sysfs_ddb_delete() error: potential NULL dereference 'fw_ddb_entry'.

Signed-off-by: Adheer Chandravanshi <adheer.chandravanshi@qlogic.com>
Signed-off-by: Vikas Chaudhary <vikas.chaudhary@qlogic.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>