phy: ti: j721e-wiz: Enable reference clock output in cmn_refclk_<p/m>

phy: ti: j721e-wiz: Enable reference clock output in cmn_refclk_<p/m>

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. In order to drive the refclk out from the SERDES
(Cadence Torrent), PHY_EN_REFCLK should be set in SERDES_RST of WIZ.
Model PHY_EN_REFCLK as a clock, so that platforms like AM642 EVM can
enable it.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Link: https://lore.kernel.org/r/20210310120840.16447-6-kishon@ti.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>