net: stmmac: Fix NAPI poll in TX path when in multi-queue

Commit 8fce3331

 introduced the concept of NAPI per-channel and
independent cleaning of TX path.

This is currently breaking performance in some cases. The scenario
happens when all packets are being received in Queue 0 but the TX is
performed in Queue != 0.

Fix this by using different NAPI instances per each TX and RX queue, as
suggested by Florian.

Changes from v2:
	- Only force restart transmission if there are pending packets
Changes from v1:
	- Pass entire ring size to TX clean path (Florian)

Signed-off-by: Jose Abreu <joabreu@synopsys.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Joao Pinto <jpinto@synopsys.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>