iio: core: add link file for iio_device

iio: core: add link file for iio_device

When iio device get registered, the iio device name has the
unique ID and all sysfs created under this device. The unique
id depends on the order it is called and so does nto give the
consistent deviceid for given device.

Hence add the link to point the iio device with unique name.

Change-Id: I0442de9fe27ba0c0e182b9469e5dc707dc31c850
Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Reviewed-on: http://git-master/r/391881
(cherry picked from commit 567d73c466881fcf5bbb9435d1a43e40fc9488af)
Reviewed-on: http://git-master/r/394087
Reviewed-by: Timo Alho <talho@nvidia.com>
Tested-by: Timo Alho <talho@nvidia.com>
GVS: Gerrit_Virtual_Submit