usb: gadget: u_ether: move hardware transmit to RX NAPI

usb: gadget: u_ether: move hardware transmit to RX NAPI

In order to reduce the interrupt times in the embedded system,
a receiving workqueue is introduced.
This modification also enhanced the overall throughput as the
benefits of reducing interrupt occurrence.

This work was derived from previous work:
u_ether: move hardware transmit to RX workqueue.
Which should be base on codeaurora's work.

However, the benchmark on my platform shows the throughput
with workqueue is slightly better than NAPI.

Signed-off-by: Weinn Jheng <[email protected]>
Cc: David Brownell <[email protected]>
Cc: David S. Miller <[email protected]>
Cc: Stephen Hemminger <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Manu Gautam <[email protected]>
Signed-off-by: Felipe Balbi <[email protected]>