net/sonic: Fix some resource leaks in error handling paths

A call to dma_alloc_coherent() is wrapped by sonic_alloc_descriptors().

This is correctly freed in the remove function, but not in the error
handling path of the probe function. Fix this by adding the missing
dma_free_coherent() call.

While at it, rename a label in order to be slightly more informative.

Cc: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Chris Zankel <chris@zankel.net>
References: commit 10e3cc18 ("net/sonic: Fix a resource leak in an error handling path in 'jazz_sonic_probe()'")
Fixes: 74f2a5f0 ("xtensa: Add support for the Sonic Ethernet device for the XT2000 board.")
Fixes: efcce839 ("[PATCH] macsonic/jazzsonic network drivers update")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>