net: dpaa: Fix dtsec check for PCS availability

We want to fail if the PCS is not available, not if it is available. Fix
this condition.

Fixes: 5d93cfcf

 ("net: dpaa: Convert to phylink")
Reported-by: Christian Zigotzky <info@xenosoft.de>
Signed-off-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>