net: xilinx: axienet: Fix Tx skb circular buffer occupancy check in dmaengine xmit

net: xilinx: axienet: Fix Tx skb circular buffer occupancy check in dmaengine xmit

In Dmaengine flow, driver maintains struct skbuf_dma_descriptor rings each
element of which corresponds to a skb. In Tx datapath, compare available
space in skb ring with number of skbs instead of skb fragments.
Replace x * (MAX_SKB_FRAGS) in netif_txq_completed_wake() and
netif_txq_maybe_stop() with x * (1 skb) to fix the comparison.

Fixes: 6a91b846af85 ("net: axienet: Introduce dmaengine support")
Signed-off-by: Suraj Gupta <suraj.gupta2@amd.com>
Reviewed-by: Sean Anderson <sean.anderson@linux.dev>
Link: https://patch.msgid.link/20250521181608.669554-1-suraj.gupta2@amd.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>