bnxt_en: reverse order of TX disable and carrier off

A TX queue can potentially immediately timeout after it is stopped
and the last TX timestamp on that queue was more than 5 seconds ago with
carrier still up.  Prevent these intermittent false TX timeouts
by bringing down carrier first before calling netif_tx_disable().

Fixes: c0c050c5 ("bnxt_en: New Broadcom ethernet driver.")
Signed-off-by: Edwin Peer <edwin.peer@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>