bnx2x: Safe bnx2x_panic_dump()

The bnx2x panic dump spills a lot of information from the driver's
fastpath, but may be called while some of the fastpath is uninitialized.

This patch verifies that pointers are already allocated before dereferencing
them to prevent possible kernel panics.

Signed-off-by: Yuval Mintz <Yuval.Mintz@qlogic.com>
Signed-off-by: Ariel Elior <Ariel.Elior@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>