ionic: squelch unnecessary fw halted message

Since the heartbeat check will already have complained about
the firmware status, don't bother complaining about the
DEVCMD failing.  We'll keep the print message but demote it
to a debug messages so that we normally no longer see it.

Signed-off-by: Shannon Nelson <snelson@pensando.io>
Signed-off-by: David S. Miller <davem@davemloft.net>