net: gemini: Fix memory leak in gmac_setup_txqs

In the implementation of gmac_setup_txqs() the allocated desc_ring is
leaked if TX queue base is not aligned. Release it via
dma_free_coherent.

Fixes: 4d5ae32f ("net: ethernet: Add a driver for Gemini gigabit ethernet")
Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>