phy: add phy_find_by_mask/phy_connect_dev

It is useful to be able to try a range of
possible phy addresses to connect.

Also, an ethernet device is not required
to use phy_find_by_mask leading to better
separation of mii vs ethernet, as suggested
by Andy Fleming.

Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>