of: Remove nested function

Some toolchains dislike nested function definition, so we define function match
outside of of_phy_find_device.

Signed-off-by: Jérôme Pouiller <jezz@sysmic.org>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>