[FS_ENET]: Fix module build.

If fs_enet is build as module, on PPC_CPM_NEW_BINDING platforms
mii-fec/mii-bitbang should be build as module, as well. On other
platforms, mii-fec/mii-bitbang must be included into the main module.
Otherwise some symbols remain undefined. Additionally, fs_enet uses
libphy, so add a select PHYLIB.

  Building modules, stage 2.
  MODPOST 5 modules
ERROR: "fs_scc_ops" [drivers/net/fs_enet/fs_enet.ko] undefined!
make[1]: *** [__modpost] Error 1
make: *** [modules] Error 2

Signed-off-by: Jochen Friedrich <jochen@scram.de>
Signed-off-by: David S. Miller <davem@davemloft.net>