bnx2x: Prevent NULL pointer dereference in kdump

In scenarios in which a previous driver was removed without proper cleanup
(e.g., kdump), it is possible for the chip to generate an interrupt without
any apparent reason once interrupts are requested.

Due to an erroneous initialization of resources, some of the bnx2x structs
which are required for interrupt handling are initialized only after an
interface's interrupt is requested from the OS.

As a result, once such a spurious interrupt occurs, it will cause a NULL
pointer dereference - the driver will access those structs in its interrupt
handling routine.

This patch change the interrupt request scheme so that bnx2x would only
request interrupts from the kernel after it has finished initializing
all the inner structs required for interrupt handling.

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>