net: ll_temac: Fix missing tx_pending check in ethtools_set_ringparam()

net: ll_temac: Fix missing tx_pending check in ethtools_set_ringparam()

The function ll_temac_ethtools_set_ringparam() incorrectly checked
rx_pending twice, once correctly for RX and once mistakenly in place
of tx_pending. This caused tx_pending to be left unchecked against
TX_BD_NUM_MAX.
As a result, invalid TX ring sizes may have been accepted or valid
ones wrongly rejected based on the RX limit, leading to potential
misconfiguration or unexpected results.

This patch corrects the condition to properly validate tx_pending.

Fixes: f7b261bfc35e ("net: ll_temac: Make RX/TX ring sizes configurable")
Signed-off-by: Alok Tiwari <alok.a.tiwari@oracle.com>
Link: https://patch.msgid.link/20250710180621.2383000-1-alok.a.tiwari@oracle.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>