liquidio: fix kernel panic when NIC firmware is older than 1.7.2

Pre-1.7.2 NIC firmware does not support (and does not respond to) the "get
speed" command which is sent by the 1.7.2 driver (for CN23XX-225 cards
only) during modprobe.  Due to a bug in older firmware (with respect to
unknown commands), this unsupported command causes a cascade of errors that
ends in a kernel panic.

Fix it by making the sending of the "get speed" command conditional on the
firmware version.

Signed-off-by: Rick Farrington <ricardo.farrington@cavium.com>
Signed-off-by: Felix Manlunas <felix.manlunas@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>