phy: cadence-torrent: Add support to drive refclk out

phy: cadence-torrent: Add support to drive refclk out

cmn_refclk_<p/m> lines in Torrent SERDES is used for connecting external
reference clock. cmn_refclk_<p/m> can also be configured to output the
reference clock. Model this derived reference clock as a "clock" so that
platforms like AM642 EVM can enable it.

This is used by PCIe to use the same refclk both in local SERDES
and remote device. Add support here to drive refclk out.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Reviewed-by: Swapnil Jakhade <sjakhade@cadence.com>
Link: https://lore.kernel.org/r/20210310120840.16447-7-kishon@ti.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>