dm: core: remove type 'static' of function uclass_get_device_tail()

Uclass API provides a few functions for get/find the device.
To provide a complete function set of uclass-internal functions,
for use by the drivers, the function uclass_get_device_tail()
should be non-static.

Signed-off-by: Przemyslaw Marczak <p.marczak@samsung.com>
Cc: Simon Glass <sjg@chromium.org>
Acked-by: Simon Glass <sjg@chromium.org>