be2iscsi: set the boot_kset pointer to NULL in case of failure

In beiscsi_setup_boot_info(), the boot_kset pointer should be set to
NULL in case of failure otherwise an invalid pointer dereference may
occur later.

Cc: <[e-mail]>
Signed-off-by: Maurizio Lombardi <[e-mail]>
Reviewed-by: Johannes Thumshirn <[e-mail]>
Reviewed-by: Jitendra Bhivare <[e-mail]>
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/scsi/be2iscsi/be_main.c

···
 	scsi_host_put(phba->shost);
 free_kset:
 	iscsi_boot_destroy_kset(phba->boot_kset);
+	phba->boot_kset = NULL;
 	return -ENOMEM;
 }