CNS3xxx: Fix PCI cns3xxx_write_config()

CNS3xxx: Fix PCI cns3xxx_write_config()

BugLink: http://bugs.launchpad.net/bugs/1580754
commit 88e9da9a2a70b6f1a171fbf30a681d6bc4031c4d upstream.

The "where" offset was added twice, fix it.

Signed-off-by: Krzysztof Hałasa <khalasa@piap.pl>
Fixes: 498a92d42596 ("ARM: cns3xxx: pci: avoid potential stack overflow")
Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>