bnxt_en: Fix tx push race condition.

bnxt_en: Fix tx push race condition.

Orabug: 23221795

Set the is_push flag in the software BD before the tx data is pushed to
the chip.  It is possible to get the tx interrupt as soon as the tx data
is pushed.  The tx handler will not handle the event properly if the
is_push flag is not set and it will crash.

Signed-off-by: Michael Chan <michael.chan@broadocm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit b9a8460a08a1e0150073cda3e7a0dd23cb888052)
Signed-off-by: Brian Maly <brian.maly@oracle.com>