Revert "Set accept_ra_rt_info_max_plen to 64 before enabling IPv6 interfaces"

On second thought, let's set accept_ra_rt_info_m**_plen in 
Netd (InterfaceController::initializeAll())

This reverts commit 25870a2c.

Change-Id: I22b000623bb852e375385d4aae789d007e84ba3d