net: phy: Define init routine and register generic phy driver

This patch define init routine for generic phy driver and registers it
using phy_register as this generic phy driver also needs to be relocated
incase of manual reloc.

Signed-off-by: Siva Durga Prasad Paladugu <siva.durga.paladugu@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>