bnx2x: Fix fastpath structures when memory allocation fails

When allocating Tx queues, if for some reason
(e.g., lack of memory) allocation fails, driver will incorrectly
calculate the pointers of the various queues.

This patch repositions all pointers in such a case to point at
sequential structures in memory, allowing the bnx2x macros to
be used correctly when accessing them.

Signed-off-by: Yuval Mintz <yuvalmin@broadcom.com>
Signed-off-by: Ariel Elior <ariele@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>