bnxt_en: Add coalescing support for tx rings.

bnxt_en: Add coalescing support for tx rings.

Orabug: 23221795

When tx and rx rings don't share the same completion ring, tx coalescing
parameters can be set differently from the rx coalescing parameters.
Otherwise, use rx coalescing parameters on shared completion rings.

Adjust rx coalescing default values to lower interrupt rate.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit dfc9c94a83909f4be80e5d0c67e79793830aa312)
Signed-off-by: Brian Maly <brian.maly@oracle.com>