UPSTREAM: staging: gdm72xx: Set up parent link in sysfs for gdm72xx devices

UPSTREAM: staging: gdm72xx: Set up parent link in sysfs for gdm72xx devices

This patch uses SET_NETDEV_DEV to set up a 'device' parent link in sysfs
(e.g. /sys/class/net/wm0/device) for a gdm72xx device.

Signed-off-by: Paul Stewart <pstew@chromium.org>
Signed-off-by: Ben Chan <benchan@chromium.org>
Cc: Sage Ahn <syahn@gctsemi.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 54bc1ff1daa86353ab07191b7fdde05e6b3844b1)

Change-Id: I795bb6c47df3b66d4272e8e455340ff369342757
Reviewed-on: https://gerrit.chromium.org/gerrit/22961
Reviewed-by: Paul Stewart <pstew@chromium.org>
Commit-Ready: Ben Chan <benchan@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>