phy: cadence-torrent: Model reference clock driver as a clock to enable derived refclk

phy: cadence-torrent: Model reference clock driver as a clock to enable derived refclk

When reference clock driver is enabled, either derived or received refclk
is output on cmn_refclk_p/m. Update the reference clock driver
implementation by modelling reference clock driver as a "clock" with
derived reference clock set as its default parent. The support for
received reference clock will be added in a separate patch.

Signed-off-by: Swapnil Jakhade <sjakhade@cadence.com>
Link: https://lore.kernel.org/r/20210922123735.21927-4-sjakhade@cadence.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>