net: dsa: check master device before put

net: dsa: check master device before put

BugLink: http://bugs.launchpad.net/bugs/1744121
[ Upstream commit 3eb8feeb1708c7dbfd2e97df92a2a407c116606e ]

In the case of pdata, the dsa_cpu_parse function calls dev_put() before
making sure it isn't NULL. Fix this.

Fixes: 71e0bbde0d88 ("net: dsa: Add support for platform data")
Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>