bnx2x: cache-in compressed fw image

Re-request fw from fs may fail for different reasons, once the fw was
loaded we won't release it until driver is removed.

This also resolves the boot problem when initial fw is located on initrd,
but rootfs is still unavailable, in this case device reset will fail due
to absence of fw files.

Signed-off-by: Dmitry Kravkov <dmitry@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>