phy: Add phy driver support for xilinx PCS/PMA core

Add phy driver support for xilinx PCS/PMA core

Signed-off-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
Signed-off-by: Kedareswara rao Appana <appanad@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>