tegra20: complete periph_id enum

Most Tegra boards output the ULPI reference clock on pad DEV2.

Complete the periph_id enum so that we are able to enable this
clock output circuit.

Signed-off-by: Lucas Stach <dev@lynxeye.de>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Warren <twarren@nvidia.com>