RFC: Rename iio_{allocate,free}_device to iio_device_{alloc,free}

[Lars-Peter Clausen <lars@metafoo.de>]

Currently we have two pairs of functions which respectively are used to
allocate/register and unregister/free a iio devices. The first pair is
iio_allocate_device, iio_device_register and the second pair is
iio_device_unregister, iio_free_device. So what can be seen is, that there
is a bit of inconsistency here as to where to put the "device" in the
function name.

So in order to streamline the API I propose to rename iio_free_device to
iio_device_free and iio_allocate_device to iio_device_alloc (alloc instead
of allocate to be more in sync with other in kernel APIs e.g.
platform_device_alloc).

If nobody sees any problems or has any objections I'll send a patch.

- Lars