gianfar: Revive fixed link support

Since commit fe192a49

 ("Rework gianfar
driver to use of_mdio infrastructure") the fixed-link support is
broken, the driver oopses at init_phy():

  Unable to handle kernel paging request for data at address 0x000000e4
  Faulting instruction address: 0xc01cf298
  Oops: Kernel access of bad area, sig: 11 [#1]
  [...]
  NIP [c01cf298] init_phy+0x80/0xdc
  LR [c01cf250] init_phy+0x38/0xdc
  Call Trace:
  [cf81fe80] [c01d1cf8] gfar_enet_open+0x6c/0x19c
  [cf81fea0] [c024494c] dev_open+0xfc/0x134
  [cf81fec0] [c0242edc] dev_change_flags+0x84/0x1ac
  [cf81fee0] [c0399ee0] ic_open_devs+0x168/0x2d8
  [cf81ff20] [c039b2e8] ip_auto_config+0x90/0x2a4
  [cf81ff60] [c0003884] do_one_initcall+0x34/0x1a8

This patch fixes the oops, and removes phy_node checks, and adds a call
to of_phy_connect_fixed_link() if a phy isn't attached..

Also, remove an old fixed-link code that we don't use any longer.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: David S. Miller <davem@davemloft.net>