net: ti: icssg: Fix XSK zero copy TX during application wakeup

net: ti: icssg: Fix XSK zero copy TX during application wakeup

emac_xsk_xmit_zc() handles tx xmit for zero copy and gets called
inside napi context. User application wakes up the kernel while
initiating the transmit which triggers napi to start processing
the tx packets. The num_tx check inside emac_tx_complete_packets()
returns early if no packet transfer happen hindering the call
to emac_xsk_xmit_zc(). Remove this check to let application
wakeup initiate zero copy xmit traffic.

Add __netif_tx_lock() to ensure that the TX queue is protected
from concurrent access during the transmission of XDP frames.
This fixes netdev watchdog timeout for long runs.

Fixes: e2dc7bfd677f ("net: ti: icssg-prueth: Move common functions into a separate file")
Signed-off-by: Meghana Malladi <m-malladi@ti.com>
Link: https://patch.msgid.link/20260618100348.2209907-1-m-malladi@ti.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>