tc35815: Use generic PHY layer

Convert the tc35815 driver to use the generic PHY layer in
drivers/net/phy.  Also rename 'boardtype' to 'chiptype' which hould be
more appropriate.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>