net: bcmgenet: decouple flow control from bcmgenet_tx_reclaim

The bcmgenet_tx_reclaim() function is used to reclaim transmit
resources in different places within the driver.  Most of them
should not affect the state of the transmit flow control.

This commit relocates the logic for waking tx queues based on
freed resources to the napi polling function where it is more
appropriate.

Fixes: 1c1008c7 ("net: bcmgenet: add main driver file")
Signed-off-by: Doug Berger <opendmb@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>