sparc: Fix sbus_alloc_coherent error handling.

Order of kfree and free_pages were swapped in the error handling.

Signed-off-by: Kristoffer Glembo <kristoffer@gaisler.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: David S. Miller <davem@davemloft.net>