[SCSI] bnx2fc: Release the reference to hba only after the interface is destroyed

Prematurely decrementing the reference may lead to cmd_mgr becoming NULL with
the cmds are still active.

Signed-off-by: Nithin Nayak Sujir <nsujir@broadcom.com>
Signed-off-by: Bhanu Prakash Gollapudi <bprakash@broadcom.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>