net: ethernet: cpsw: switch to devres allocations

This patch cleans up the allocation and error unwind paths, which
allows us to carry less information in struct cpsw_priv and reduce the
amount of jump labels in the probe functions.
Signed-off-by: Daniel Mack <zonque@gmail.com>
Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>