phy: cadence-torrent: Adopt Torrent nomenclature

- Change private data struct cdns_dp_phy to cdns_torrent_phy
- Change module description and registration accordingly
- Generic torrent functions have prefix cdns_torrent_phy_*
- Functions specific to Torrent phy for DisplayPort are prefixed as
  cdns_torrent_dp_*

Signed-off-by: Swapnil Jakhade <sjakhade@cadence.com>
Signed-off-by: Yuti Amonkar <yamonkar@cadence.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>