bnx2x: limit fw delay in kdump to 5s after boot

Commit 12a8541d "bnx2x: Delay during kdump load" added a 5 seconds
delay to bnx2x's probe function in the kdump case to let the firmware
realize the old driver is gone.

The problem with the delay is that it is per-device, so if you have
several bnx2x NICs in NPAR mode, the delays can accumulate to minutes.

Fix it by adjusting the delay so that we do not wait more than
necessary, i.e. no more delaying after 5 seconds of kernel boot time.

Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>