The CPSW has two slaves. When one of them fails to setup continue
anyway with the other one. This fixes a crash in the beaglebone black
which only has one slave connected. The code doesn't find a phy on
the second slave and bails out, but the error path is broken: It frees
the private data structures which contains used resources.

Reported-by: Philippe Leduc <ledphilippe@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>