bnx2fc: fix memory leak and potential NULL pointer dereference.

If bnx2fc_allocate_hash_table() for some reasons fails, it is possible that the
hash_tbl_segments or the hash_tbl_pbl pointers are NULL.
In this case bnx2fc_free_hash_table() will panic the system.

this patch also fixes a memory leak, the hash_tbl_segments pointer was never
freed.

Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Acked-by: Eddie Wai <eddie.wai@broadcom.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>