dt-bindings: phy: cadence-torrent: Add defines for refclk driver

Add defines for refclk driver used to route the refclk out of torrent
SERDES.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Link: https://lore.kernel.org/r/20210721155849.20994-6-kishon@ti.com