fsl_pq_mdio: Clean up tbi address configuration

The code for setting the address of the internal TBI PHY was
convoluted enough without a maze of ifdefs. Clean it up a bit
so we allow the logic to fail down to -ENODEV at the end of
the if/else ladder, rather than using ifdefs to repeat the same
failure code over and over.

Also, remove the support for the auto-configuration. I'm not aware of
anyone using it, and it ends up using the bus mutex before it's been
initialized.

Signed-off-by: Andy Fleming <afleming@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>