phy: cadence-torrent: Add PCIe(100MHz) + USXGMII(156.25MHz) multilink configuration

Add support for dual reference clock multilink configurations. Add
register sequences for PCIe(100MHz) + USXGMII(156.25MHz) multilink
configuration.

Signed-off-by: Swapnil Jakhade <sjakhade@cadence.com>
Signed-off-by: Roger Quadros <rogerq@kernel.org>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>