fec: Do not access unexisting register in Coldfire

Commit 55cd48c8 ("net: fec: stop the "rcv is not +last, " error
messages") introduces a write to a register that does not exist in
Coldfire.

Move the FEC_FTRL register access inside the FEC_QUIRK_HAS_RACC 'if' block,
so that we guarantee it will not be used on Coldfire CPUs.

Reported-by: Greg Ungerer <gerg@uclinux.org>
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>