net: ethernet: et131x: Use GFP_KERNEL instead of GFP_ATOMIC when allocating tx_ring->tcb_ring

There is no good reason to use GFP_ATOMIC here. Other memory allocations
are performed with GFP_KERNEL (see other 'dma_alloc_coherent()' below and
'kzalloc()' in 'et131x_rx_dma_memory_alloc()')

Use GFP_KERNEL which should be enough.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>